Risk of Estrogen-Driven Malignancies in Females on 5-Alpha Reductase Inhibitors

This study examined the risk of estrogen-driven malignancies in females using 5-alpha reductase inhibitors (5aRI) for alopecia, analyzing data from 145 million patients and including 5,156 matched pairs. It found a 27.6% decreased risk of breast cancer after 10 years of 5aRI use and a 31.9% decrease in lifetime breast cancer risk. There was no significant difference in the risk of ovarian or endometrial cancer between users and non-users. The results suggest that 5aRI use does not increase the risk of estrogen-driven malignancies and may offer protection against breast cancer.