Effects of Finasteride on Steroid Production and Gene Expression in Male Fathead Minnow and Medaka

The study investigated the effects of Finasteride (FIN) on steroid production and gene expression in male fathead minnow and medaka, exposing them to 1 mg/L of FIN for up to 21 days. Results showed that FIN significantly reduced plasma dihydrotestosterone (DHT) concentrations in fathead minnows and upregulated testes srd5a2 gene expression in both species, indicating that DHT plays a crucial role in fish similar to mammals. The study highlights the conserved molecular targets in the androgen biosynthesis pathway across species. Internal plasma concentrations of FIN were higher than water concentrations after 48 hours, emphasizing the need to understand internal exposure for assessing pharmacological effects in fish. The findings suggest potential read-across between humans and fish through 5α-reductase inhibition.