Effects of In Utero Exposure to Finasteride on Androgen-Dependent Reproductive Development in Male Rats

In the 2003 study, pregnant rats were administered finasteride, a drug that inhibits the conversion of testosterone to dihydrotestosterone (DHT), at doses of 0.01 to 100 mg/kg/day from gestation days 12 to 21. The male offspring were evaluated for reproductive development until postnatal day 90. The study found dose-dependent decreases in anogenital distance (AGD) and increases in nipple retention, indicating inhibited DHT-mediated development. At the highest dose, there were significant reproductive malformations, including absent prostate lobes, ectopic testes, and hypospadias. The lowest observed adverse effect level (LOAEL) for permanent changes was 0.1 mg/kg/day. The study concluded that in utero exposure to finasteride resulted in permanent changes in the reproductive system of male rats, with minimal effects on testosterone-mediated development. The number of pups per dose group ranged from 23 to 33.