Thursday, October 3, 2013

Battle of the Sexes: Men Found to Have Higher Levels of BPA in Their Blood Than Women

There are many studies examining the levels of Bisphenol A (BPA) and other endocrine disruptors present in the environment, and a large number of studies investigating the mechanisms or pathways these chemicals may take to wreak havoc on living things. 

BPA and several other endocrine disruptors have been linked to a whole host of health problems, including but not limited to cancer, low testosterone and low sperm motility, miscarriages, and birth defects.

How much do I really have in my body?

Sure, that’s all fine and dandy if you can tell me just how a certain amount of BPA can affect my health, but really, is BPA even present in these amounts in my body?  Or are the amounts required to elicit these hazardous consequences much too large to have any meaning biologically?

In 2002, a team of researchers in Japan set out to answer a few simple, yet highly important questions: 1) How much BPA is present in human blood; 2) Are there any differences in BPA levels between men and women?; and 3) What are the relationships between BPA and sex hormones present in our bodies?

Guinea Pigs

Well, not ACTUAL guinea pigs, but real human beings…a group of 14 healthy women, a group of 16 women with diagnosed polycystic ovary syndrome (PCOS), and a group of 11 healthy men were recruited to give blood serum samples for this study. 

What they found…

What this team of researchers found was that serum BPA levels were significantly higher in healthy men than in healthy women.  Serum BPA levels in these healthy men were 1.49 +/- 0.11 ng/mL, while serum BPA levels in healthy women were 0.64 +/- 0.10 ng/mL (CONVERT TO PPM…..).  Also, they found that serum BPA levels significantly correlated with both free testosterone levels and total testosterone levels.  Interestingly, serum BPA levels were not significantly correlated with any other sex-related hormone, including luteinizing hormone, follicle stimulating hormone, prolactin, and estradiol.  Finally, these levels found in both men and women were HIGHER than the levels reported to cause problems

Why do the men have it all?

Why did the men in this study have a significantly higher level of the chemical in their blood than women?  Well, this study didn’t explicitly study the “why” side of things; however, a few possibilities come to mind.

One thought is that BPA may somehow disrupt the feedback control of testosterone hydroxylation.  As the body produces testosterone, it produces enough up until a “magic point” where a feedback mechanism kicks in and tells the body to “hey, man!  There’s too much testosterone here!  Back off!”.  Once levels drop to a certain level, production of testosterone can start again and so the cycle continues.  What might be going on here is that BPA somehow manages to interfere with this feedback mechanism, and somehow manages to “confuse” the system so that it no longer instructs the body to stop making testosterone.  Therefore, the body will just keep making more and more, and as a result of the BPA exposure, will not send the message for the excess to be destroyed.

Another possible mechanism is that BPA acts as a sort of antagonist for the naturally produced sex-hormones in the body, in this case; testosterone.  BPA could be competing against testosterone for binding onto the androgen receptor, thereby somehow disrupting the androgen-estrogen balance within the body. 

You didn’t answer my question: Why do men have higher levels of BPA in their system than women?

 Well, I did answer it in a round-about way above, but again, this was more of an “observational” study and didn’t explicitly examine the mechanisms or reasons behind these differences.  However, one thing that should jump out to you is this:  BPA was found to be significantly correlated to testosterone levels and no other sex-related hormone in the body.  Men have higher levels of testosterone by nature than women.  Therefore, one can guess that because men have greater levels of testosterone in their bodies and BPA is significantly correlated with testosterone levels, then men will have greater levels of BPA in their blood.  Voila!

More detailed studies will shed further light on this subject, but in the meantime, the results of this study should give a tiny clue as to how endocrine disruptors behave in the human body.

Source: Takeuchi, T., and Tsutsumi, O. 2002. Serum Bisphenol A Concentrations Showed Gender Differences, Possibly Linked to Androgen Levels. Biochemical and Biophysical Research Communications 291: 76-78.

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