dutasteride

An antiandrogen (5α-reductase inhibitor) primarily used to treat moderate to severe benign prostatic hyperplasia in men, an enlarged prostate not associated with cancer. A few months may be required before benefits occur.
It is usually taken by mouth.

5α-reductase inhibitors inhibit 5α-reductase (enzyme), which is involved in the metabolic transformations of a variety of endogenous steroids, that include preventing conversion of testosterone (androgen) to dihydrotestosterone (more potent androgen).

5α-reductase isoforms I and II reduce progesterone to 5α-dihydroprogesterone and deoxycorticosterone to dihydrodeoxycorticosterone, that may lead to neurosteroid metabolites with effect on cerebral function. These neurosteroids act as potent positive allosteric modulators of GABAA receptors, having antidepressant, anxiolytic, prosexual, and anticonvulsant effects.
That is why 5α-reductase inhibitors may cause depression.

(Indications)
• benign prostatic hyperplasia (enlarged prostate not associated with cancer)
• scalp hair loss in men
• hormone therapy in transgender women

(Side effects)
• sexual dysfunction (e.g. erectile dysfunction, decreased sex drive)
• depression
• gynecomastia (enlarged breasts)

(Contraindications)
• pregnancy: It interferes with the sexual development of male fetuses as an antiandrogen.