Estrogen in birth control diminishes sex organs in male rats.
A number of permanent oddities – such as deformed penises and smaller reproductive organs that were caused by exposure to the same estrogen found in birth control pills – contributed to the infertility seen in adult male rats exposed during the time when their reproductive organs were forming.
Recent animal research suggests that women who continue to take birth control pills well into pregnancy may unwittingly skew their boys’ reproductive development in ways that could diminish their sons’ fertility. Similarly, exposure to environmental chemicals that act like estrogen – such as certain pesticides and industrial chemicals, including bisphenol A – may also affect these organs if the exposure occurs during a sensitive time of development.
Researchers compared the effects of different levels of the estrogen used in birth control pills. Their results are published in the journal Toxicological Sciences.
They found that exposure to low levels of the hormone during development detrimentally affects the reproductive organs and fertility in the male rats tested. The rats have smaller testicles and other reproductive organs if exposed to the low amount of estrogen a women may use daily in certain birth control pills. Testosterone hormone levels are also reduced. Exposure to just ten times that amount of estrogen permanently deforms penises and causes infertility in the adult animals.
This research is relevant to humans because more than 50 million women worldwide take contraceptive pills. Of those, 3 to 4 percent may take them into the second trimester of pregnancy, the authors say.