Thursday, 16 February 2017

Free Article Series: Fertility and Endometriosis

There are lots of articles being published on endometriosis all the time, (for example there were over a thousand articles either directly or indirectly related to endometriosis published last year) the main reason this blog exists is because the vast majority of these studies never get read by people actually affected by the disease. Mostly this is because these studies are published in scientific journals and/or hidden behind online paywalls only accessible to people in academic institutions, and even then the studies are written in very dry, scientific terms. 

Sometimes research in endometriosis makes it to the news, but often this is conveyed by journalists who, as well meaning as they can be, often misinterpret or exaggerate scientific information. I aim to write about the latest endometriosis research in a way anyone can read and understand, but there is so much being published all the time it difficult to cover it all here. Fortunately some research is made available for free for anyone to read, so I’m starting a series providing free articles on a certain theme each time. This time I’m going to be listing some of the most relevant, free articles concerning one of the major facets of endometriosis; fertility, how it affects women, how surgery affects pregnancy rate, how fertility therapy can help women with endometriosis and several other areas. Just click on the title of each article to be taken to the full text.

As mentioned though some of the articles are written in a rather dry prose and include a lot of detail about scientific methods and analysis that may not be relevant to the lay reader, so I would say the most important parts of some articles are the introductions/background and the discussion/conclusions, so feel free to skip to those parts to get the most interesting information. I’ve included the summary for each article so you can see which ones are of most interest to you.

Authors: González-Comadran M, Schwarze JE, Zegers-Hochschild F, Souza MD, Carreras R, Checa MÁ.
Published In: Reproductive Biology and Endocrinology. 2017 Jan 24;15(1):8. doi: 10.1186/s12958-016-0217-2.
Summary: Reproductive outcomes among women undergoing IVF and diagnosed with endometriosis-associated infertility do not differ significantly from women without the disease. Although women with endometriosis generate fewer oocytes, fertilization rate is not impaired and the likelihood of achieving a live birth is also not affected.

Authors: Nezhat C, Li A, Abed S, Balassiano E, Soliemannjad R, Nezhat A, Nezhat CH, Nezhat F.
Published In: Journal of the Society of Laproendoscopic Surgeons. 2016 Jul-Sep;20(3). pii: e2016.00053. doi: 10.4293/JSLS.2016.00053
Summary: In our patient population, 87.1% of patients with a chief concern of symptomatic fibroids also had a diagnosis of histology-proven endometriosis, which affirms the need for concomitant diagnosis and intraoperative treatment of both conditions. Overlooking the coexistence of endometriosis in women with symptomatic leiomyoma may lead to suboptimal treatment of fertility and persistent pelvic pain. It is important for physicians to be aware of the possibility of this association and to thoroughly evaluate the abdomen and pelvis for endometriosis at the time of myomectomy or hysterectomy in an effort to avoid the need for reoperation.

Authors: Ke X, Qian H, Kang L, Wang J, Xie Y, Cheng Z.
Published In: International Journal of Clinical and Experimental Medicine. 2015 Nov 15;8(11):21703-6. eCollection 2015
Summary: Surgery can improve the symptom remission rate and fertility of patients. Postoperative drug therapy does not improve the chance of pregnancy

Authors: Nesbitt-Hawes EM, Campbell N, Maley PE, Won H, Hooshmand D, Henry A, Ledger W, Abbott JA.
Published In: Biomed Research International. 2015;2015:438790. doi: 10.1155/2015/438790. Epub 2015 Jul 12.
Summary: These data provide information to women with suspected severe disease preoperatively concerning their likely postoperative fertility outcomes. Ours is a population with severe endometriosis, rather than an infertile population with endometriosis, so caution needs to be applied when applying these data to women with fertility issues alone.

Authors: Xu B, Guo N, Zhang XM, Shi W, Tong XH, Iqbal F, Liu YS.
Published In: Scientific Reports. 2015 May 29;5:10779. doi: 10.1038/srep10779
Summary: Endometriosis, a pathological condition in which the endometrium grows outside the uterus, is one of the most common causes of female infertility; it is diagnosed in 25-40% of infertile women. The mechanism by which endometriosis affects the fertility of females remains largely unknown. We examined the ultrastructure of oocytes from patients with minimal or mild endometriosis and control females undergoing in vitro fertilization (IVF) treatment. Our results suggest that decreased oocyte quality because of impaired mitochondrial structure and functions probably an important factor affecting the fertility of endometriosis patients.

Authors: Mavrelos D, Saridogan E.
Published In: Journal of Obstetrics and Gynaecology of India. 2015 Feb;65(1):11-6. doi: 10.1007/s13224-014-0652-y.
Summary: Endometriosis is a common condition affecting a significant proportion of women in their reproductive age. Apart from the impact of endometriosis on the quality of life of these patients, it also can have an impact on the potential of these women to have a family. The options for treating women with endometriosis desiring a family include surgery or assisted reproduction techniques. The choice of treatment will depend on the stage of disease and the characteristics of the couple seeking help. We review here the latest evidence on the management of endometriosis in women desiring fertility and describe our current practice.

Authors: Borghese B, Sibiude J, Santulli P, Lafay Pillet MC, Marcellin L, Brosens I, Chapron C.
Published In: PLoS One. 2015 Feb 13;10(2):e0117387. doi: 10.1371/journal.pone.0117387.
Summary: The influence of intrauterine environment on the risk of endometriosis is still controversial. Whether birth weight modifies the risk of endometriosis in adulthood remains an open question. For this purpose, we designed a case-control study involving 743 women operated on for benign gynecological indications from January 2004 to December 2011. Among patients with LBW, the risk is almost two-times higher to develop DIE. This association could reflect common signalling pathways between endometriosis and fetal growth regulation. There is also the possibility of a role played by placental insufficiency on the development of the neonate's pelvis and the occurrence of neonatal uterine bleeding that could have consequences on the risk of severe endometriosis.

Authors: Fadhlaoui A, Bouquet de la Jolinière J, Feki A.
Published In: Frontiers of Surgery. 2014 Jul 2;1:24. doi: 10.3389/fsurg.2014.00024.
Summary: Endometriosis is defined as the presence of endometrial-like tissue (glands or stroma) outside the uterus, which induces a chronic inflammatory reaction. Although endometriosis impairs fertility, it does not usually completely prevent conception. The question of evidence based-medicine guidelines in endometriosis-associated infertility is weak in many situations. Therefore, we will highlight in this issue where the challenges are.

(endometriosis covered in chapter 10)
Authors: Various
Summary: This guideline offers best practice advice on assisting people of reproductive age who have problems conceiving. It is estimated that infertility affects about one in seven heterosexual couples in the UK. Since the original NICE guideline on fertility was published in 2004 there has been a small increase in the prevalence of fertility problems and a greater proportion of people now seeking help for such problems. The main causes of infertility in the UK are (percentage figures indicate approximate prevalence): ovulatory disorders (25%); tubal damage (20%); factors in the male causing infertility (30%); uterine or peritoneal disorders (10%). In about 25% of cases infertility is unexplained, with no identified male or female cause. In about 40% of cases disorders are found in both the man and the woman. Uterine or endometrial factors, gamete or embryo defects, and pelvic conditions such as endometriosis may also play a role. Given the range of causes of fertility problems, the provision of appropriate investigations is critical. These investigations include semen analysis; assessment of ovulation, tubal damage and uterine abnormalities; and screening for infections such as Chlamydia trachomatis and susceptibility to rubella. Once a diagnosis has been established, treatment falls into three main types: medical treatment to restore fertility (for example the use of drugs for ovulation induction); surgical treatment to restore fertility (for example laparoscopy for ablation of endometriosis); assisted reproduction technology (ART) – any treatment that deals with means of conception other than vaginal coitus; frequently involving the handling of gametes or embryos.

Authors: Jin X, Ruiz Beguerie J.
Published in: Taiwan Journal of Obstetrics and Gynecology. 2014 Sep;53(3):303-8. doi: 10.1016/j.tjog.2013.02.004.
Summary: The use of laparoscopic surgery in the treatment of subfertility related to minimal endometriosis may increase the chances of future pregnancy and live birth

Authors: Dong X, Liao X, Wang R, Zhang H.
Published in: International Journal of Clinical and Experimental Pathology. 2013 Aug 15;6(9):1911-8.
Summary: Except reduced implantation rate in stage III-IV endometriosis group, no differences were found in other pregnancy parameters. This study suggests that IVF/ICSI yielded similar pregnancy outcomes in patients with different stages ofendometriosis and patients with tubal infertility. Therefore, IVF/ICSI can be considered as an effective approach for managingendometriosis-associated infertility.

Authors: Macer ML, Taylor HS.
Published in: Obstet Gynecol Clin North Am. 2012 Dec;39(4):535-49. doi:10.1016/j.ogc.2012.10.002.
Summary: Endometriosis has been associated with infertility; however, the mechanisms by which it affects fertility are still not fully understood. This article reviews the proposed mechanisms of endometriosis pathogenesis, its effects on fertility, and treatments of endometriosis-associated infertility. Theories on the cause of the disease include retrograde menstruation, coelomic metaplasia, altered immunity, stem cells, and genetics. Endometriosis affects gametes and embryos, the fallopian tubes and embryo transport, and the eutopic endometrium; these abnormalities likely all impact fertility. Current treatment options of endometriosis-associated infertility include surgery, superovulation with intrauterine insemination, and in vitro fertilization. We also discuss potential future treatments for endometriosis-related infertility.

Authors: Carvalho LF, Below A, Abrão MS, Agarwal A.
Published in: Revista de Associacao Medica Brasileira (1992). 2012 Sep-Oct;58(5):607-14.
Summary: Endometriosis, a highly prevalent gynecological disease, can lead to infertility in moderate to severe cases. Whether minimal stages are associated with infertility is still unclear. The purpose of this systematic review is to present studies regarding the association between pregnancy rates and the presence of early stages of endometriosis.

Authors: Lerchbaum E, Obermayer-Pietsch B.
Published In: European Journal of Endocrinology. 2012 May;166(5):765-78. doi: 10.1530/EJE-11-0984.
Summary: Vitamin D has been well-known for its function in maintaining calcium and phosphorus homeostasis and promoting bone mineralization. There is some evidence that in addition to sex steroid hormones, the classic regulators of human reproduction, vitamin D also modulates reproductive processes in women and men

Authors: Bulletti C, Coccia ME, Battistoni S, Borini A.
Published in: Journal of Assisted Reproduction and Genetics. 2010 Aug;27(8):441-7. doi: 10.1007/s10815-010-9436-1.
Summary: Endometriosis is a debilitating condition characterized by high recurrence rates. The aetiology and pathogenesis remain unclear. Typically, endometriosis causes pain and infertility, although 20-25% of patients are asymptomatic. The principal aims of therapy include relief of symptoms, resolution of existing endometriotic implants, and prevention of new foci of ectopic endometrial tissue. Current therapeutic approaches are far from being curative; they focus on managing the clinical symptoms of the disease rather than fighting the disease. Specific combinations of medical, surgical, and psychological treatments can ameliorate the quality of life of women with endometriosis. The benefits of these treatments have not been entirely demonstrated, particularly in terms of expectations that women hold for their own lives. Although theoretically advantageous, there is no evidence that a combination medical-surgical treatment significantly enhances fertility, and it may unnecessarily delay further fertility therapy. Randomized controlled trials are required to demonstrate the efficacy of different treatments.

Access to articles is provided by US National Library of Medicine and National Institutes of Health as well as individual publishers

Friday, 3 February 2017

Endometriosis - Going Back to Basics

This is a blogpost I’ve been meaning to do for a while now. In this blog I mostly write about specific research with a pretty narrow focus, but what about the general information about endometriosis that people might want to know? There are of course many good resources out there in the vast expanse that is the internet, but at the same time there is misinformation and bad advice out there as well. With that in mind I’m going to try and put together a list of, what I think, is useful information for anyone starting their journey into endo, or those who simply want to know more about it. As the title says it is very much the basics so I’ve provided some links throughout this post to longer articles that cover certain topics in more detail. If I’ve missed out anything glaringly obvious, or there is something you’d like to know and want me to add to this list, add a comment to the bottom of this post, or tweet me @endoupdateblog

To begin with then, let’s start with the most obvious and basic question

What is Endometriosis?

Endometriosis, those six unwieldy syllables, means different things to different people. To the suffer it is a malign, invisible tormentor. To the doctors/surgeons it is a minefield of trial and error.  To the researcher it is an enigmatic mystery to be solved. But I doubt you came here to read about the philosophical descriptions of endometriosis (and if you did, sorry, maybe I’ll cover that in a different blog post). I’m guessing you want to know what endometriosis physically is. Before I do that however, some prerequisite knowledge is needed about the female reproductive system.

If you’re reading this you either possess, or at the very least know about, the uterus (womb).
Image Courtesy of By OpenStax College [CC BY 3.0 (], via Wikimedia Commons

Inside the uterus is a thick muscular layer called the myometrium, this is responsible for contractions during labour and those wonderful menstrual cramps I know women are so fond of [sarcasm]. The inner lining layer of the uterus is called endometrium, which is the ‘functional’ part. The endometrium is the part of the uterus that grows and sheds with each menstrual cycle and is responsible for the bleeding that I know women are so fond of [more sarcasm]. I’ve written before about how the endometrium and the menstrual cycle work so I won’t cover that here. The point to take away is that the endometrium is inside the uterus and during the menstrual cycle it grows and then breaks down and sheds off during menstruation.

Endometriosis is defined as patches of endometrium-like tissue (called endometriotic lesions) outside the uterus. Now I use the term ‘endometrium-like’ purposefully here. You see the patches of tissue that comprise endometriosis resemble the endometrium when looked at under a microscope. However several studies, which have analysed endometriosis and the endometrium at the molecular level, have shown there are numerous differences between the two tissue types. In any case endometriosis is often referred to as ectopic endometrium (literally meaning ‘out of place endometrium), or endometriotic tissue, whereas the normal endometrium is often referred to as the eutopic endometrium. Endometriosis is still responsive to hormones in a similar manner to the normal endometrium, so the theory goes that, throughout the menstrual cycle, endometriosis grows and bleeds, but unlike the normal endometrium, the blood has nowhere to go because its inside the pelvic cavity. Whether or not endometriosis does actually ‘bleed’ is somewhat contentious, but the presence of endometriotic lesions does certainly lead to inflammation, pain, subfertility and a myriad of other horrible symptoms depending on the extent and location of endometriosis.

Almost as important as what endometriosis is, is what endometriosis is not. Endometriosis is not an infection of any kind, it’s not communicable, it’s not a cancer and is not fatal, however just because something is not fatal, doesn’t mean it can’t take your life away.

Also you cannot define endometriosis purely by its symptoms, endometriosis is not just painful periods. Sure, some women with endometriosis have painful periods, some don’t, some women have pain so severe it is literally disabling, but endometriosis is a complex condition that requires holistic and often personalised approach. For example, one woman with endo may have severe pelvic pain, depression, anxiety and bowel pain, whereas another woman may have no pain or psychological symptoms, but is infertile, these two cases would require very specific and different approaches.  

Which brings me to my next point: the types of endometriosis.

Endometriosis is subject to a grading system depending on the extent and type of the disease, which you can read about in more detail here. Endometriosis is usually categorised into four stages (minimal, mild, moderate and severe), which depend on the type, extent and location of the disease.  Although the stages sound fairly descriptive of the disease, that is not necessarily the case. The stage of disease doesn’t always correlate with the symptoms experienced, so a woman with severe disease can have no symptoms and a women with minimal disease can have debilitating symptoms and vice versa.

In the broadest terms there are three types of endometriosis. Superficial endometriosis are lesions that can be found anywhere around the pelvic area. However, they are most frequently found on the surface of organs/ligaments/structures of the pelvis and can be as small as to be almost invisible to the naked eye, or about as large as a pea and any size in between. This type of endo comes in a variety of different colours: red lesions are considered to be ‘active’ in that they produce inflammatory factors and can have a dense network of blood vessels supplying them, blue/black lesions are similar to red but are seen as an older form of the disease, white lesions are thought to represent even older and inactive endometriosis, but often have a lot of scar tissue associated with them which can pull or restrict the surrounding tissue leading to pain. There is some evidence to suggest that superficial endometriosis undergoes a transition from red > blue > white, but how and at what speed this transition occurs isn’t known.

The next type is endometriotic cysts. These are most commonly found on the ovaries and are cysts filled with old blood that takes on a brown colour, giving them the undeservedly pleasant name ‘chocolate cysts’. These cysts can grow to be quite large, ranging from a few centimetres on average, to massive cysts in very rare cases. Because they affect the ovaries, endometriotic cysts tend to be associated with decreases in fertility, fortunately there are treatment options available to restore fertility to women with endometriosis associated subfertility, but I’ll be discussing that later on.

The third type is deeply infiltrating endometriosis (DIE). As the name suggests these are lesions that are actually dug into the tissue of the pelvis. Because DIE can penetrate into tissues it can be quite challenging for surgeons to remove completely and has been known to cause some of the more severe symptoms associated with endometriosis.

Although endometriosis is mostly found in the pelvis, there are other, rarer forms of the disease that can be found elsewhere, this is termed ‘extra-pelvic’ or ‘extra-genital’ endometriosis. I’ve tried to list all the places endometriosis can be found in the human body (that we know of) and it would seem it can be found almost anywhere. However, it is definitely worth remembering that endometriosis outside the pelvis is extremely rare, some cases of endometriosis in places you wouldn’t expect to find it have only been reported once.

What are the symptoms of endometriosis?

To put it one way; everything, nothing and all things in between. In less simplistic terms endometriosis can present with no symptoms at all. Some women are only diagnosed when they are having an operation for another condition, or when there is an investigation for something linked to endo, like fertility issues. However, for those who do get symptoms, the most common one is pain, pain pain pain and more pain, plus other things as well because apparently all that pain isn’t enough. The most common pain symptom of endometriosis is dysmenorrhoea (pronounced DIS-MEN-OH-RE-AH), which is defined as excessively painful periods that cause interference to the daily life of the sufferer and is experienced by half to two-thirds of women with endometriosis at some point in their life.

Now even I know that ‘normal’ periods (if there is such a thing) aren’t like the tampon commercials make them out to be; it’s not all blue liquid and laughing while playing beach volleyball. However, if your periods are causing you to regularly miss school/work or social occasions because they are so painful, this is not ok and could very well be a sign of an underlying medical condition, like endometriosis. I can’t emphasise this point enough because there is a massive delay in diagnosis experienced by women with endometriosis. On average this delay is 7-9 years, depending on where you live and what healthcare you have access to, so there can be shorter or longer diagnosis times. Either way such a long diagnostic delay is utterly unacceptable. Can you imagine going to a doctor, in excruciating pain, and being told “sure, I’ll tell you what’s wrong with you, in seven years”? Chances are you wouldn’t be happy about that. Unfortunately that is the reality many women with endo have to face.

A factor that doesn’t help the diagnostic delay is that the most accurate way to diagnose endometriosis is with a surgical operation called laparoscopy, where cameras are inserted into the pelvic cavity and the surgeon has a good examination of the pelvic organs. If the surgeon finds something suspicious they can take a biopsy and send it away to be analysed to confirm the presence of endometriosis. Finding endometriosis, of course, is dependent on the skill and experience of the surgeon.

There are non-invasive imaging techniques that can aid in the diagnosis of endometriosis. Ultrasound, for example, can be useful in finding ovarian endometriotic cysts, whilst MRI can identify cysts, distortion of the pelvic organs caused by endometriosis and can look inside organs without the need for surgery. However, these techniques have nowhere near the accuracy of actually looking into the pelvis with a camera. Unfortunately there is no accurate blood test for endometriosis, however many research groups are working hard on this, not as a replacement for laparoscopy, but as a means of identifying women at high risk of endometriosis and reducing diagnostic delay.

From the studies I’ve read and the women I’ve spoken to, the most significant contributor to this diagnostic delay is invalidation of the sufferer’s symptoms. Some women with endometriosis, particularly young girls with symptoms of the disease, are told by medical professionals that painful periods are ‘normal’. Women are often prescribed painkillers or contraceptive pills to manage their symptoms. Whilst these treatments can offer some relief, they can be ineffective in some women. These women can often face further struggle to get their symptoms taken seriously and can end up being labelled as hysterical (hysteria literally translates as ‘suffering of the womb’) and can have their symptoms ascribed to psychological rather than physical conditions.

It is true that women with endometriosis are at an increased risk of being diagnosed with mood disorders, depression and anxiety. However, studies have also shown that after successful surgery to remove endometriosis, depressive symptoms regress and overall emotional wellbeing increases. This is extremely important to note as it shows that the physical symptoms of endometriosis can be causative of the psychological symptoms, not the other way around. Of course it is possible that psychological disturbances could lead to alteration in pain perception, meaning that a vicious cycle can be established where pain leads to depression, which leads to increased pain sensitivity, which leads to more depression and so on and so on, but at the head of it all is the disease itself. 

Another of the common pain symptoms associated with endometriosis is chronic pelvic pain, which affects around a third of women with endo. This differs from dysmenorrhoea in that it doesn’t necessarily refer to pelvic pain during menstruation and can be caused by numerous other diseases or conditions. Chronic pelvic pain can be continuous or intermittent and can be associated with a variety of factors, for example exercise, specific foods or certain activities, or it may just come on randomly.

Painful sex (also known as dyspareunia – pronounced DIS-PAR-YOO-NEE-AH) is one of the symptoms of endometriosis that doesn’t get much attention despite the fact it affects a third to two-thirds of women with endometriosis.  Part of the reason dyspareunia gets little acknowledgement is that it is a very personal and private matter, which can understandably be difficult to talk about openly. Studies have indicated that women who have endometriosis (particularly DIE) behind the vagina, in an area known as the rectovaginal septum, are more likely to suffer from dyspareunia. One of the most challenging aspects of this symptom is the effect it can have on relationships. I myself know how important it is to have an open dialogue with partners to ensure they understand the physical limitations endometriosis can place on the sufferer, but I’ll be discussing more on that later.

There are whole host of others symptoms that can be associated with endometriosis that vary from person to person in terms of frequency and severity. Some of these include: leg pain, bloating, painful urination, painful bowel movements, heavy menstrual bleeding, spotting in between periods and fatigue.   

Endometriosis is also the proverbial misery that loves company. Rarely does a woman have endometriosis and nothing else.  I wrote a whole blog post on the subject, which you can read here, that gives details on some of the most informative studies looking at which other conditions are, and are not, found more frequently in women with endo.

As you can probably tell from reading this far, there are an awful lot of potential presentations and symptoms of endometriosis, some women may present with nearly all of them, some women may present with none. Each person’s journey with endometriosis will have elements that are shared with many other sufferers, but at the same time will have elements that are very specific to their own personal experience of the disease. This unfortunately, also makes endometriosis all the more difficult to diagnose and treat effectively.

Who gets endometriosis?

That’s a good question. Unfortunately there is very little good quality information available that could give us an answer. We do know that endometriosis affects around 1 in 10 women of reproductive age, but it would seem that endometriosis can affect anyone, of any age (I’ve read case reports of endometriosis in infants and women in their seventies, although I should point out these cases are very, very rare) and of any race/socioeconomic background.

Studies have shown that women with a family history of endometriosis are more likely to have the disease. This implies there is a strong genetic component to endometriosis and that the risk can be passed from parent to child. This doesn’t mean that a woman with endometriosis is guaranteed to pass the disease to her daughter; rather the chance of her daughter having endometriosis is increased. Endometriosis can also appear in women with no family history, the causes for this ‘spontaneous’ form of the disease are still hotly debated, in fact no-one truly knows why endometriosis occurs at all, but there are plenty of ideas, some of which I’ll be discussing later.

We do see that women aged 21-35 are more likely to be diagnosed than women of other age brackets. This has led to the misconception that endometriosis is a ‘career woman’s disease’, which afflicts those women who delay childbearing to further their career. This notion is not only insulting to women, it is also factually incorrect.

In my view there are two main reasons that endometriosis appears to be more common in in women in their mid-twenties to early thirties. Firstly, the symptoms of endometriosis tend to appear in adolescence, if you factor in the aforementioned diagnostic delay of 7-9 years then it becomes apparent diagnosed occurs in your mid-twenties.  Secondly, the notion that delaying childbirth is somehow responsible for causing endometriosis is simply wrong. There is some evidence to suggest that, during pregnancy, the symptoms of endometriosis can subside. However, symptoms can rapidly return after giving birth. Having children is in no way a cure for endometriosis. It is also incredibly insensitive to suggest to a woman, who has a condition characterised by high rates of fertility problems, that delaying childbearing is the cause for said condition, or that having children is the solution to it. That is like telling a person in a wheelchair that not walking is the cause for their paralysis and it can be cured by going for a jog.

From what I have learnt over the years it would seem that the reason endometriosis is so commonly diagnosed in women of a particular age range, is not because of the choices or lifestyle of the women in question, but because of lack of awareness and education about endometriosis. This is endemic, not only amongst the public, but also in the medical community. There are a great deal of myths and misinformation about endometriosis (several of which I have wrote about previously) and women with endo often have to become experts on the subject themselves in order to justify their illness to others.

I have encountered this ignorance personally, mostly in the form of bizarre theories about what causes endometriosis and how it should be treated (my favourite one to date was the doctor, yes a doctor, that said endometriosis can be caused by wearing your trousers too tight!). The most important weapon any woman with endometriosis can have is knowledge. Resources and information are plentiful, but the best piece of advice I could give is always ask for evidence. If someone suggests a treatment, ask what studies support their assertion. Where does the evidence come from? Are there studies that show how effective it is? Asking just a few simple questions like this can quickly reveal which claims have no basis in evidence.

Fortunately there are many great organisations out there that are fighting for better awareness and education for endometriosis and they are doing a great job of it. I myself have noticed a distinct improvement in endometriosis awareness in the last 10 years, so the future looks bright.

What are the treatments?

There are many treatments for endometriosis, but no cure. That itself is a contentious statement and lies in the tricky semantics of the word ‘cure’. Some would argue that surgery which removes all endometriosis and gets rid of its symptoms is a cure, but with endometriosis there is always a chance the disease could recur, maybe not for years or decades, but there is still a chance and if a person’s disease relapses, then they were never truly cured. We could get bogged down in this argument about meaning all day, so let’s not do that. Instead let’s discuss what the treatments for endometriosis are and their effectiveness.

Endometriosis is not a ‘one disease, one treatment’ affair, there are many treatment options open for women with endometriosis and it is often quite a minefield of trial and error to find the right one. Something that definitely needs to be considered is that endometriosis is rarely a disease of just one symptom. Endometriosis requires a holistic approach to therapy that considers all aspects and impact the disease has on a person’s life.

Most women when they are first diagnosed, or when they are suspected to have endometriosis, are prescribed painkillers. These vary in effectiveness with some women finding minor relief and some women finding no relief at all. In others the pain can be so severe as to require very strong painkillers like codeine or morphine. Painkillers though do nothing to treat the disease itself, merely to reduce the symptoms, if pain symptoms are severe then further treatment needs to be sought.

There are several types of hormonal medication that women with endometriosis may be offered, the most common ones are:

·         Birth control pills (BCPs) contain a form of estrogen and a progestin (which acts like progesterone). These are also known as ‘combined’ pills as they combine two hormone types in one pill. The rationale for using this treatment is that endometriosis needs estrogen to remain active, the pill reduces the amount of estrogen in the body to a constant low level. You may wonder why, if endometriosis needs estrogen, does the pill have estrogen in it? Estrogen is added to prevent some side effects like breakthrough bleeding and actually works to make the pill a more effective as a contraceptive. It is thought that endometriosis requires a certain threshold of estrogen to remain active. The combination pill contains such a low dose of estrogen that it is below this threshold and therefore safe for treating endometriosis.

There are many different brands and formulations of birth control pills so it’s always worth asking your doctor what the exact composition of your medication is (although this should also be provided on the instruction insert that comes with your medications). The way in which the formulation of the pill varies determines whether it is monophasic or multiphasic. Monophasic pills contain the same levels of each hormone in each pill, multiphasic drugs on the other hand, deliver different levels of hormones over the course of a month. The multiphasic drugs were developed in order to reduce some of the unwanted side effects of monophasic drugs.

·         Progestin only pills (POPs), or mini-pills, only contain a progestin; these tend to be used if a patient finds the side effects of the combination pill intolerable. At present there is no evidence to suggest whether POPs or BCPs are better for the treatment of endometriosis, but because of how differently each woman may react to each drugs, it is difficult to say which is best. Medical guidelines suggest BCPs and POPs are used as a first line treatment for endometriosis and can be safely taken for long periods of time, provided the side effects are tolerable. Progestins can also be given as an injection (the most well-known being depo-provera), and via an intrauterine device (commonly known as the coil), which provides more local delivery of the drug, in theory reducing the side effects. Injections and the coil have the advantage of providing long term therapy without having to take pills every day, but the disadvantage that, if side effects become problematic, the drug cannot be stopped as easily as pills can. It is always a good idea to discuss with your doctor which form of treatment is right for you, particularly as medications designed to prevent conception aren’t ideal of you want to conceive anytime soon.

·         Gonadotrophin releasing hormone analogues (GnRHa) are, as the name suggests, drugs that mimic the effect of GnRH in the body. These drugs work by dramatically reducing the production of estrogen by the ovaries, essentially putting the body into a false menopause and are generally used as a second line treatment for endometriosis. Although GnRHa’s have been shown to have some beneficial effects in reducing the symptoms of endometriosis (however evidence shows their benefit is comparable to that of other treatments like the coil and BCPs) and improving conception if given for 3 months prior to trying to conceive, they often come with a hefty amount of side effects and cannot be taken for longer than 6 months without increasing the risk of causing permanent health problems. The menopause-like state they induce can result in side effects like mood swings, weight changes, hot flashes, vaginal dryness and loss of bone density to name but a few, which means this is where careful consideration needs to be made in terms of downsides weighed up against benefits.  A popular option offered to women to reduce the side effects of this treatment is ‘add back’ therapy. This is essentially hormone replacement therapy (HRT), where a small dose of estrogen is given to alleviate the side effects of estrogen withdrawal. You may wonder why or how estrogen can be given to women when estrogen is implicated in the growth of endo. It is believed there is a threshold level of estrogen needed to stimulate the endo, any dose of estrogen given below that level shouldn’t cause the growth of endometriosis. Nevertheless any women on HRT who experiences a relapse of endometriosis symptoms needs to consult her doctor as soon as possible.

·         Aromatase inhibitors haven’t been used to treat endometriosis for a very long time so there isn’t as much evidence about their effectiveness as other drugs. Sometimes endometriosis doesn’t respond to other forms of treatment mentioned above. This can be due to the endometriotic lesion having an enzyme called ‘aromatase’ active in it. Endometriosis relies on estrogen to stay active, therefore most treatments either limit or reduce the amount of estrogen the ovaries produce. However if endometriosis has the aromatase enzyme, it can synthesise its own estrogen, essentially becoming independent of the hormones produced by the ovaries and becoming a disease that does not respond to first and second line treatments (this is known as refractory endometriosis). For this kind of endometriosis aromatase inhibitors may be offered. This treatment is especially useful for older women with endometriosis, who are nearing (or past) the menopause, or who may be ineligible for surgery. These drugs do drastically reduce estrogen production in the body though, so can have similar side effects to GnRH analogues, therefore monitoring side effects, particularly in older patients, needs to be undertaken carefully.

Something important to take into consideration though is that, if the symptoms of endometriosis don’t respond well to initial treatment, other conditions must be accounted for too. Endometriosis and adenomyosis are found very frequently together as are adhesions in women with endometriosis, therefore it is important that doctors conduct a thorough investigation to determine exactly what conditions they are dealing with and how best to treat them.

·         Alternative or complimentary therapies are often sought by women suffering the symptoms of endometriosis to try in conjunction with other treatments. Again I would reiterate that doing your research is the most important thing to do, especially where alternative therapies are concerned, mainly because they are not regulated or subject to the same standards of quality control and testing as conventional medicine. One approach that many women benefit from is dietary changes. This doesn’t work for everyone, but if there is the possibility of some relief from the symptoms of endo, it’s always worth giving a try. There are lots of different resources out there that can advise with endo diets and specific recipes and programs to follow, which at the core suggest: eliminating red meat, gluten, diary, processed foods and refined sugars, whilst increasing intake of green vegetables, fruit and omega-3 fatty acid containing foods, so have a look around and see what you can find. One extra bit of advice though, remember there is no such thing as a miracle cure and always be wary of those with an agenda to push or a product to sell, anyone who truly has your best interests at heart will offer advice freely.

·          One of the main concerns of many women with endometriosis is the effect the disease can have on fertility. The true effect of endometriosis on fertility is not one of clear distinction. The proportion of infertile women with endometriosis is reported to be anywhere between 9-50%. Although, before going any further, we need to define infertility and subfertility. Infertility is defined as not being able to conceive at all, however many women with endometriosis are in fact subfertile, meaning that they are able to conceive, but it is much more difficult. It is reported that monthly chances of conception drop from around 25% to 2-10% in women with endo, making becoming pregnant problematic. There are also problems that can occur during pregnancy to consider, some evidence suggests complications like preterm birth, preeclampsia and placenta previa are more common in women with endo, but as long as these risks are recognised by doctors and midwives then any risk to the mother and child should be minimised. One of the most obvious causes of reduced fertility is endometriosis affecting the ovaries (although endo can also have effects on hormonal balance and the structure of the fallopian tubes which affects fertility as well). The presence of endometriosis does not only affect the ovaries; even if an egg is fertilised it must implant in the endometrium to develop. The endometrium has a very narrow timeframe when implantation of the developing embryo can occur, called the ‘window of implantation’.  There have been many studies that have concluded there are several differences in the endometrium of women with and without endometriosis. The big question is though, what clinical implications do those differences have?  Studies have shown that several genes are altered during the window of implantation in the endometrium of women with endometriosis and this may contribute to the reduced fertility some women with endo experience. There is a much more in depth article on the effect of endometriosis on pregnancy outcomes you can read, for free, here.

Women suffering from fertility issues may decide to undergo assisted reproduction technology (ART) to aid in achieving pregnancy. ART can refer to therapies such as fertility medication and in vitro fertilisation (IVF), which are the more common forms of ART. The studies that have been conducted on the use of ART in women with endometriosis have found that having endo doesn’t appear to alter the success of these treatments.

Medical therapy does, and always will, have its uses in managing endometriosis, and hopefully will only improve as the years go by and our understanding of the disease and the progression of technology marches ever onward. However, at present medical therapies don’t get rid of the disease itself, rather they aim to alleviate the symptoms. The best long term results from the symptoms of endo come from surgery to physically remove the disease. In order to diagnose and surgically treat endometriosis a laparoscopy is the most common type of surgery performed. This involves inserting several ‘arms’ (which are like metal tubes) into the pelvis that have various attachments like a camera and manipulators or surgical scissors or a laser etc. Depending on how complex the surgery is and what needs to be done depends on how many tools the surgeon will have to use. Usually with laparoscopy you will end up with several small (about 1-1.5cm long) incisions around the pelvic area.

The advantage of laparoscopy is that endometriosis can be diagnosed and treated during the same operation, if time permits, though some women will have to have a diagnostic laparoscopy separate from a therapeutic one.  The different surgical procedures can be classified in two ways depending on the extent of the surgery that needs to be done.

·         Conservative surgery is a term given to surgical procedures that generally spare the removal of whole organs, instead focussing on removal of the disease itself. This can be done using two methods; ablation of the lesions and excision of the lesions. Ablation involves using heat to burn away and destroy the lesions (often using a laser), whereas excision actually cuts out and removes the lesions (which can also be done using a laser). Both excision and ablation have their place in endometriosis surgery, ablation can be more useful if cutting out an area of endometriosis could prove dangerous. For example, when it comes to operating on the ovaries, cutting out a cyst (cystectomy) may lead to damage of the underlying tissues of the ovary, leading to reduced fertility. For example, due to the nature of endometriotic ovarian cysts, when surgically removing them 54-69% of ovarian tissue can be removed too compared to only 6% when dealing with other ovarian cyst types. Some studies have suggested that ablating ovarian endometriotic cysts may increase the rate future pregnancy, especially when using IVF.

 There are few studies that actually examine the difference between the effectiveness of ablation and excision for endometriosis. Those that have been done suggest that both techniques are roughly equally effective for the treatment of minimal endometriosis, but excision is the preferable option for deep lesions and ovarian endometriotic cysts, as it leads to better symptom improvement and less likelihood of the disease recurring, but as mentioned above careful consideration needs to be made when weighing up the outcomes desired by the patient.

·         Radical surgery involves the whole or partial removal of organs for the treatment of endometriosis. This can be as a result of deep endometriosis infiltrating the bowel (which can occur in 6-35% of deep endo cases) or the urinary tract (which can occur in 1-5% of deep endo cases). Other forms of radical surgery include hysterectomy, salpingectomy (removal of the fallopian tubes) and oophorectomy (removal of one or both ovaries). You may wonder why a hysterectomy would be beneficial for endometriosis, after all the lesions are the cause of the symptoms and they are most frequently found around the uterus, not on it. As mentioned before, adenomyosis and endometriosis are two conditions found very frequently together and unfortunately hysterectomy is the most effective treatment for adenomyosis. Hysterectomy though is not a viable treatment option for endometriosis alone and, although some insist on grasping to the idea that hysterectomy is somehow a cure for endometriosis, this is simply not the case.

Careful consideration needs to be made when deciding the optimal surgical approach for different types of endometriosis and the conditions associated with it. For example, although the risk is still low, radical surgery does carry an increased risk in operative and post-operative complications, some of which can be severe, which is why it is always important to discuss the surgical procedure you are going to undergo with your surgeon.

What causes endometriosis?

And the award for the most contentious question in endometriosis goes to…this one! The absolute truth of the matter is that no-one knows for certain what causes endometriosis. There are a few theories though, which at best explain certain aspects of the disease, but as yet there isn’t a unified theory of endometriosis. I’ll give a brief overview of some of the most popular theories here, if however you would like to read an in depth article on the history of endometriosis you can do, here.

Perhaps the most widely known theory is that of retrograde menstruation. This theory was developed in the 1920’s by a U.S physician by the name of John Sampson. He postulated that, during regular menstruation, most of the blood and lining of the uterus (the endometrium) would exit the body in the usual manner, but some would travel up through the fallopian tubes and out into the peritoneal space (which is where the reproductive organs sit). Once there the endometrial fragments implant on and around the surface of the reproductive organs and form growths that are fed by the hormone produced by the body and result in what we call endometriosis.

At the time this theory made an awful lot of sense. Observing endometriosis down the microscope, there are obvious visual similarities between endometriosis and the normal endometrium. Additionally the process of endometrial fragments travelling up and out from the uterus (retrograde menstruation) is known to occur in 90% of women. Furthermore endometriotic lesions seemed to react to hormones in a similar manner to the normal endometrium (i.e. growing when exposed to estrogen). Not only this but over the years using animal models of endometriosis, fragments of the endometrium were injected into the peritoneal space of monkeys, mice and rats to mimic retrograde menstruation and, lo and behold, endometriotic lesions formed. So it’s easy to understand why this theory gained so much traction and popularity. However, as the march of progress continued and research methods became more advanced, some holes in this theory became apparent.

Perhaps the most obvious question to ask would be – if retrograde menstruation is the cause of endometriosis, and retrograde menstruation happens in 90% of women, why don’t 90% of women have endometriosis? It is known that women with endo show alterations in their immune system that could allow endometriosis to form. In particular, women with endo show alterations in the immune cells that would normally clear away the refluxed endometrial fragments, making it easier for the cells to implant around the reproductive organs.

Detailed analysis of endometriotic lesions however, has shown that there are distinct differences in the genetic, protein and gene regulation profiles and sensitivity to hormones between endometriosis and the normal endometrium indicating they are quite different tissue types. Certain types of endometriosis are difficult to explain with the retrograde menstruation theory, in particular endometriosis outside the pelvic area. Endometriosis has been found in almost every organ in the body (as I’ve written about previously), although it should be noted that some cases of extra-pelvic endo are extremely rare, sometimes only one case exists. Perhaps some of the most damning evidence against retrograde menstruation comes from case reports of endometriosis in unborn foetuses, women who cannot menstruate, animals that don’t menstruate  and in men (although there have only been a handful of male endometriosis cases reported worldwide).

The evidence of endometriosis like patches in unborn foetuses certainly suggests endometriosis, or at the least the propensity to develop it, is something you are born with. Familial and genetic studies support this as it has been found that there are genetic alterations more common in women with endo and women with a first degree relative with endometriosis, are much more likely to develop the disease too.

 So what could the answer be? Several other theories have been proposed about how endometriosis could arise. One suggested that, under the influence of hormones like estrogen, normal tissue in the pelvis could transform into endometrial-like tissue. This has led to researchers pointing the finger at environmental pollutants that mimic the effect of estrogen in the body. Although some research has been done into this area, the results are far from conclusive. Experiments done in the

Other theories have taken this further by suggesting that, during the very early development of the reproductive organs in the foetus, some of the tissue that would go on to become the uterus gets ‘misplaced’. When a girl reaches puberty and hormone levels rise, these patches of tissue mature into endometriotic lesions. This explanation would certainly account for the cases of endometriosis in men as all of them have been men undergoing hormone therapy for prostate cancer. You can find a much more detailed analysis of explanations regarding the origin of endometriosis here.

Of course, it could be there is no single cause for endometriosis and there are multiple mechanisms by which the disease can arise. What we do know about the origin of endometriosis can be summarised as

-          Most women with endometriosis report the symptoms appearing in adolescence, particularly near puberty, suggesting hormones play a role in the onset of disease symptoms
-          Endometriosis appears to be a condition you are born with, or you are born with an increased risk of developing the disease. There is nothing you do in life to ‘get’ or ‘catch’ endometriosis, that is down to fate alone.
-          Endometriosis displays a strong genetic component and seems to run in families, this can obviously be a concern for mothers with daughters. However, there is nothing one can do to prevent someone having endometriosis, women with endometriosis need an effective support network and that should start at home. So I’ve always said, the best thing a young girl with endometriosis can have is a mother who understands.
-          Although endometriosis can run in families, it can also occur spontaneously in women with no family history. These cases are more of a mystery and no one really knows how or why they occur. Of course there are plenty of other immune conditions, neurological conditions and cancers, which have a genetic component and can just arise seeming out of nowhere, so it could very well be that endometriosis is no different.
-          Endometriosis doesn’t appear to affect any race, or ethnic group disproportionally like other disease such as fibroids or diabetes. However no large studies have been conducted to investigate whether this is true or not.
-          Other medical conditions such as immune conditions seem to be more frequent in women in endo, suggesting whatever influences the development of endometriosis also influences the risk of other conditions as well

Information for Partners and Family Members

I’ve been the partner of a woman with endometriosis for 17 years at the time I’m writing this and also I’ve been the son of a woman with endometriosis all my life; it has been the inspiration for me to study endometriosis professionally and why I write this blog.

Over the years there are few lessons that I’ve learnt that I hope others will find useful in supporting someone with endometriosis. I should point out that I can only talk from the male partners perspective, because that is what I am, I hope this advice is applicable to everyone, but if there are specific issues or experiences you know of that apply to same sex couples, or if you are a trans person with endo, I’d love to hear about your experiences either in the comments or message me @endoupdateblog on twitter.

Perhaps the most important thing I’ve learnt is that many women with endo have to face continual invalidation of their symptoms from people in general and medical professionals sometimes. Endometriosis is not a visible disability, many women with endo look fine (don’t ever say to someone with endo “but you look fine”) which makes it difficult to know exactly what the condition can do unless you’ve had a great deal of personal experience with it. So simply believing someone with endo when they describe what’s wrong, or how they are feeling is very important. Another point is understanding the limitations that endometriosis can put on someone. Endo can result in pain during certain times and ‘flare ups’ that mean the person cannot do everyday activities and this is especially frustrating for them, so it is essential to not make them feel blamed or at fault; it is the disease’s fault, not there’s. I found that an individual’s endometriosis is like a separate entity that has its own moods and character, if you come to know that character you know how best to respond to it, so you don’t feel helpless and actually feel helpful.

Feelings of guilt at not being able to go out and socialise or do everyday things, are common in women with endo and other chronic conditions, therefore be mindful of how you respond to someone’s limitations so as not to cause or worsen feelings of guilt. That is not to say you need to be treading on eggshells or offering pity to people with endo, just that a bit of patience, understanding and consideration will go a long way.

Of course as with many chronic illnesses intimacy between partners can become an issue. This can be especially the case with endometriosis as the condition can lead to symptoms that make sex too painful and the treatments can decrease libido. A partner of someone who experiences these symptoms needs to understand that sex isn’t the be all and end all of a relationship, most of you probably know that already, but women with endo can sometimes feel pressured or like they have to satisfy their partner. If this is the case it’s up to you to reassure her that intimacy isn’t just about sex and remind her of all the other wonderful things about her that are the real reason you’re together. And sometimes it might be that you both do want sex, but don’t forget that sex isn’t just one thing, there are lots and lots of things to try that can be good for both you; different positions, taking it slow, lots of foreplay, use your imagination! Be patient.

One of the most difficult aspects of being a partner or family member of someone with endo is seeing someone you love in pain but being unable to do anything about it. I’ve experienced this feeling of helplessness a lot myself, but educating yourself about the disease and how it affects the person you care about will give you real insights into things you can do to help. No, you will not be able to cure them, but learning about treatments and how that person’s endo works will allow you to have an open dialogue with them about their condition and what the little things are you can do that make a big difference. Sometimes it can as simple as knowing when to make a hot water bottle to knowing not to plan an event or activity during certain times of the month, it all helps lower the burden of endometriosis.

I can’t emphasise enough the importance of education about endometriosis, being able to talk to someone openly and frankly about their condition improves a relationship between two people by creating ways for them to talk and interact which would otherwise be shut off because of the illness. An illness like endometriosis doesn’t have to be a barrier between people, it can be the exact opposite, you’ve got to put the time and effort, but the helping someone you care about is worth it.

Further information

There are loads of other good endometriosis information sites out there, notable ones include:

If I’ve missed any sites out that you think should be on this list, add them to the comments below, links to personal blogs are also welcome, however a strict policy I have on this blog is that no adverts or links to sites containing adverts for products or services that have not been tested with an adequate level of scientific rigor will be allowed.  

Wednesday, 22 June 2016

All the Small Things

It’s always interesting/entertaining/amusing when an animal does something we think is typically human; a dog riding a bike, a cat playing Candy Crush, a hamster surfing, and thanks to the internet we can see all these things, what a time to be alive. But the other week I was surprised to hear of an animal that did something no-one thought it could do and the repercussions of this could have a major impact on the world of endometriosis research.

This was a report I read documenting the first ever observed occurrence of a species of mouse (the spiny mouse to be precise) having a menstrual cycle. Up until now the only animals we were familiar with that menstruate were primates like chimps, gorillas and humans. Other animals have different reproductive cycles characterised by different hormonal and physical changes in their reproductive organs. Most other mammals, including mice, undergo an estrous cycle. The estrous cycle, like the menstrual cycle, is still regulated by hormones such as estrogen and progesterone, but the way these hormones vary throughout the respective cycles and the effect they have, differs.

The diagram below shows how the different hormones that regulate the function of the reproductive organs changes over the human menstrual cycle and the rat estrous cycle. If you want to see how these hormones work in humans I've covered it here.

As you can see, there are quite obvious differences, but also some similarities between the two. The rat proestrus stage for example, is somewhat similar to the human day 14 and the rat day 4 resembles the human day 10, but overall they are quite distinct. In terms of the actual physical changes, menstrual animals shed their endometrium after each cycle if conception doesn’t occur. This, as some of you will all too painfully know, is having a period. Estrous animals on the other hand reabsorb the endometrium if conception doesn’t occur and, although some animals like dogs might bleed at certain times of their cycle, this is not an actual period, rather it is caused by estrogen making the blood vessels in the vagina ‘leaky’.

So the discovery of a menstrual cycle in the spiny mouse is surprising to say the least, but why is this relevant to endometriosis research? In order to study the way in which endometriosis works and develop new treatments we can grow endometriosis cells in the lab and experiment on them. Unfortunately this tells us nothing of the complexity of the disease or how endometriosis behaves in a living organism. For this researchers turn to animal models of the disease. This is usually achieved by ‘inducing’ endometriosis in a lab animal (typically estrous mice). However this is far from a perfect model of the disease. Inducing the disease in mice is achieved by transplanting either pieces of whole uterus, or pieces of the normal endometrium into the pelvis of the mice. Neither of these gives a true representation of human endometriosis, but it’s the closest thing researchers have at their disposal to study endometriosis (there are much more accurate primate models of endometriosis, but there are numerous reasons, such as cost, facilities and ethics, that prohibit the use of these animals in most research centres).

Another problem is that because normally mice don’t menstruate, the disease will not behave in mice the same way it behaves in humans due to different levels of hormones in the body. Mice can be made to have hormonal cycles like humans but this involves removing the ovaries and supplementing them with hormones and even this doesn’t represent the complexity of hormonal changes during the human cycle.

By using an animal that can menstruate, our models of endometriosis would become more accurate (in fact we may not need to induce endometriosis in these spiny mice if they develop it spontaneously, much more investigation is needed to observe this though). By extension the way we understand the disease in humans and the effectiveness with which we can develop new treatments will also become more accurate. Additionally, one of the goals that researchers work towards is reducing the number of animal experiments that are required to study any given disease. By using an animal that more closely resembles the human menstrual cycle, it would eliminate the need for performing additional procedures on lab mice to induce human-like hormonal cycles.

However, there is still a lot of work to find out exactly how similar the spiny mouse menstrual cycle is to the human one. The initial research that has been done has shown the spiny mouse cycle to be 9 days long. The human cycle is, on average, 28 days long and, interestingly, the pattern of progesterone levels in the blood across the spiny mouse cycle almost exactly matches that of the human cycle.

Although there is a lot of work still to be done investigating this unusual phenomenon, it not only has impact for endometriosis research, but also into other female reproductive conditions, like infertility, pregnancy and menstrual disorders.