Paracetamol Use During Pregnancy May Lower Fetal Testosterone

Prolonged paracetamol (acetaminophen) use by pregnant women may reduce testosterone production in their unborn baby boys, according to a new study.

Researchers at the University of Edinburgh (United Kingdom) conducted a study to test the effect of paracetamol on testosterone production in mice that carried a validated xenograft model of human testicular tissue. The researchers gave the mice a typical daily dose of paracetamol, for a period of either 24 hours or seven days, and measured the amount of testosterone produced by the human tissue an hour after the final dose of paracetamol.

The results showed that exposure to a therapeutic dose of acetaminophen for seven days reduced plasma testosterone by 45% and seminal vesicle weight—a biomarker of androgen exposure—by 18%, whereas acetaminophen exposure for just one day did not alter either parameter. The researchers clarified that plasma acetaminophen concentrations (as measured one hour after the final dose) in exposed host mice were found to be substantially below those reported in humans after a therapeutic oral dose. The study was published on May 20, 2015, in Science Translational Medicine.

“Our results suggest that protracted use of acetaminophen may suppress fetal testosterone production, which could have adverse consequences […] Prolonged use of paracetamol in pregnancy may increase the risk of reproductive disorders in male babies,” concluded study coauthor Rod Mitchell, MD, and colleagues. “We would advise that pregnant women should follow current guidance that the painkiller be taken at the lowest effective dose for the shortest possible time.”

Most common male reproductive disorders are linked to lower testosterone exposure in fetal life, although the factors responsible for suppressing fetal testosterone remain largely unknown. Recent studies have shown that reduced exposure to the hormone in the womb is linked to an increased risk of infertility, testicular cancer, and undescended testicles.

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