Prolonged exposure to acetaminophen during pregnancy may suppress testosterone production by fetal testes, according to a study conducted by investigators from the University of Edinburg, United Kingdom, that used a xenograft model in which human fetal testes were transplanted into castrated mice (van den Driesche S et al. Sci Transl Med. 2015;7:288ra80).
In mice grafted with human fetal testes that were treated with a human-relevant dose of acetaminophen (20 mg/kg) 3 times a day for 1 week, testosterone levels in the blood decreased by 45%, and weight of the seminal vesicle glands, a biomarker of testosterone exposure, fell by 18%. Acetaminophen treatment for a single day had no effect on testosterone production.
When the investigators analyzed the fetuses of pregnant rats treated with a higher dose (350 mg/kg) of acetaminophen once a day for a week, they found reduced activity of keen enzymes in the testosterone-synthesis pathway.
The authors noted that their findings are clinically important because many pregnant women use acetaminophen, which passes readily across the placenta, and there is growing evidence that common male reproductive disorders may be attributed to suboptimal fetal exposure to androgens.