Finasteride (Propecia) and dutasteride (Avodart) are prescribed for the treatment of male pattern baldness.
Finasteride and dustasteride belong to a group of drugs called "5 alpha reductase inhibitors." They block the enzyme 5 alpha reductase and decrease the levels of the potent androgen hormone DHT (dihidrotestosterone). In addition to reducing DHT, the drugs increase the levels of estrogen slightly which has raised questions from physician and researchers around the world as to whether these drugs increase the risk of breast cancer in men.
US researchers set out to examine the relationship between the use of 5 alpha reductase inhibitors and male breast cancer. They studied men using the higher 5 mg dose of finasteride used in prostate enlargement (rather than the 1 mg dose used in hair loss) and the 0.5 mg dose of dutasteride. They looked at the use of these drugs in 339 men with breast cancer and 6,780 men without breast cancer.
What were the findings and conclusions from the study?
The authors did not find an association between using 5 alpha reductase inhibitors and the development of breast cancer in men. Overall, the authors concluded that the "development of breast cancer should not influence the prescribing of 5 alpha reductase inhibitor therapy."
Bird ST et al. Male breast cancer and 5 alpha reductase inhibitors finasteride and dustasteride. J Urology; 190:1811-4