Monday, 27 February 2012

BPA and Endometriosis

One of the most troubling questions that still looms large over the heads of all of those affected by endometriosis is, where does the condition come from? More specifically, what causes endometriosis? We know that there are genetic factors that influence the risk of developing endo, so if your mother had the disease, you are more likely to have it, but if that is the case, where did your mother get it from? From her mother probably, but there has to be a point where it originated because there are many women who have no family history of endometriosis yet still develop the condition.

If we look at other complex conditions like cancer, for example, there are the familial risk factors but there are also external factors that influence the risk. For cancer there is, well, quite a lot of things really, the worst of these you can avoid simply by living a healthy lifestyle, but if you want to escape all potentially harmful substances you’ll have to seal yourself in a vacuum chamber and get buried 2000miles under the earth. So it is a reasonable question to ask whether there are any external factors that influence the development of endometriosis.

The first aspect we need to consider, when trying to answer this question, is the issue of timing of exposure. I’ve put a few posts on here that provide evidence suggesting endometriosis is something you are born with, therefore there is not much point in looking for influencing factors in grown women with well established disease. If endometriosis is indeed a condition you are born with, then exposure during the development of the foetus is probably the most important time to consider the influence of external factors.

Where do you start though when looking for potential environmental nasties? As we know endometriosis is an estrogen dependant disease, so it would make sense to look at pollutants in the environment that have the potential to mimic estrogen, one such chemical, which is known to have weak estrogenic activity, is Bisphenol-A (BPA). Before we go any further I should probably address the question of what is BPA. BPA is a chemical that is mostly used in the manufacture of plastics, so if you’ve ever used or handled or cooked with something plastic, you’ve been exposed to BPA. But is it dangerous and does exposure to BPA have any relation to endometriosis?

The trouble is it’s very difficult to measure the exposure of unborn children to environmental factors without putting the foetus at risk and I very much doubt pregnant women would be happy about being injected with a potentially harmful substance. One way around this is to perform experiments on animals, which is what one research team in Italy have done.

This study took pregnant mice and gave them, throughout their pregnancy, BPA in various doses. After the mice gave birth the pups were kept for 3 months then their ovaries were analysed to see what effect the BPA had. The results showed that mice exposed to BPA in the womb were more likely to develop damage to their ovaries. Not only that but some mice developed an endometriosis like condition.

That pretty worrying, right? Well let’s look a bit closer before we go off and start building our subterranean vacuum chamber. One of the issues with this study is the dose of BPA given; the mice in question received doses of BPA ranging from 100 to 1000 micrograms per kilogram per day. Although it sounds small, this is in fact a huge dose, likely exceeding anything any human would ever be exposed to. It’s a bit like trying to test the effect of microwaves on a potato by dropping a nuclear bomb on a farm (ok I’m exaggerating a bit there).

Then we have the age old problem of using mice as an analogue for humans. Whilst mice are surprisingly similar to humans, in a physiological respect, there are of course major differences, particularly in the reproductive systems. But there is also the difference in metabolism to take into consideration. Humans and mice metabolise BPA in different ways and this is important when considering the effect BPA has on the body. A study conducted at the Institute for Toxicology, Wurzburg University, Germany, found that humans metabolised and excreted BPA much quicker than rodents, meaning there is a much smaller chance of BPA having a harmful effect on the human body.

So is that the end of it? No need to worry about BPA? Maybe, but maybe not; there have been other studies showing that BPA levels are elevated in the blood of women with endometriosis, so perhaps women with endometriosis have a deficiency in the enzymes that metabolise BPA? Whilst that sounds like a fascinating hypothesis, other studies have shown that not to be the case and furthermore, there is no difference in the levels of urinary BPA between infertile women with endo and healthy controls, oh well so much for that idea. However, there is still no evidence concerning the effect of foetal exposure to BPA in humans and how this might relate to endometriosis risk. There have been other studies suggesting foetal BPA exposure affects childhood behaviour and brain function, however there are those that say no such association exists, so it is really difficult to come to any real conclusion here, the jury is still out on BPA.

As usual I would always encourage you to do your own research if you’re concerned about any topic, but be cautious when searching out there on the vastness of the internet. There are plenty of reactionary idiots with agendas to push and no evidence to back up their claims, a good rule of thumb I have is; if it sounds sensationalist, it’s probably not true.