Effects of Finasteride

Finasteride blocks the action of an enzyme called 5-alpha-reductase. This enzyme changes testosterone to another hormone that causes the prostate to grow or hair loss in males. It will increase testosterone levels in the body, which decreases prostate size and increases hair growth on the scalp.

It also inhibits aromatase-independent testosterone conversion into estrogenic steroids

the synthesis of estrogenic steroids was blocked by inhibition of testosterone conversion into dihydrotestosterone using a 5 alpha-reductase inhibitor finasteride, suggesting that they are generated downstream of dihydrotestosterone

This in thoery must masculinize people who take it, but it instead femnizes them. Source.

Finasteride causes certain male individuals to show symptoms of demasculinization and feminization after exposure

Why? What's happening?

1 Answer 1


Finasteride inhibits conversion of testosterone to dihydrotestosterone (DHT). This is also why it is used to prevent androgenic alopecia.

DHT is considerably more potent than testosterone in the prostate and at the androgen receptor in general. In fact DHT is the most potent endogenous androgen and also cannot be converted to oestrogen.

This makes sense, if you do not convert testosterone to a more potent form then the overall effect on the androgen receptor is reduced, despite total serum testosterone increasing.

  • Interestingly, the last linked paper mentions that Finasteride treats and decreases the risk of prostate cancer, but patients undergoing these therapies have increased rates of higher-grade cancers. Jan 2, 2022 at 8:26

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