Exposure to bisphenol A may alter hormone levels in men.

May 05, 2010

Meeker, JD, AM Calafat and R Hauser. Urinary Bisphenol A concentrations in relation to serum thyroid and reproductive hormone levels in men from an infertility clinic. Environmental Science and Technology http://dx.doi.org/10.1021/es9028292.

A new study finds associations between exposure to bisphenol A (BPA) and the blood levels of thyroid and reproductive hormones.

Bisphenol A (BPA) can affect hormone levels in animals, and some recent studies suggest the widely used compound may have similar effects in people. 

More than 90 percent of the U.S. population is exposed to BPA, most likely through diet. The chemical was first manufactured in 1891 and has since been shown to have estrogenic properties in animals.

Very few studies have examined whether BPA may affect hormone levels in humans. The results of this study are published in the journal Environmental Science and Technology and add to that growing body of research.

Many consumer products contain BPA. Most notably, it is found in some types of hard, polycarbonate plastic baby and water bottles – although many manufacturers have recently removed it from baby and children's items. The lining of food and beverage cans, some dental fillings and sealants and thermal paper may all contain BPA.

In this study, researchers measured the concentration of BPA in the urine of 167 men recruited through a Massachusetts infertility clinic and determined hormone levels in their blood. They found that men with higher urine BPA concentrations had higher blood levels of follicle-stimulating hormone (FSH) and lower levels of inhibin B. Elevated FSH and depressed inhibin B have been associated with poorer sperm quality in humans.

The study also reported a reduction of the ratio of estrogen to testosterone, possibly reflecting an abnormality in the production or elimination of these hormones.  In addition, lower thyroid-stimulating hormone (TSH) was observed when data on multiple BPA measurements were used to assess exposure, suggesting excessive thyroid hormone production (called a hyperthyroidic effect).

It is important to note that BPA and hormone levels were measured at the same time (in some cases, BPA was determined in samples collected after hormone measurement).  The possibility that hormonal status may have altered urinary excretion of BPA – rather than BPA affecting hormone levels – therefore cannot be entirely ruled out.

Results from this study are, however, supported by animal studies that show altered hormone levels in animals exposed to BPA.