Description

Finasteride, also known by its trade name Propecia, is a selective inhibitor of 5α-reductase, the enzyme responsible for converting testosterone into dihydrotestosterone (DHT), a more potent form of androgen. DHT plays a central role in the development of benign prostatic hypertrophy and androgenetic alopecia.

Finasteride works primarily by inhibiting type II and III 5α-reductase isoenzymes, reducing DHT production in the prostate and scalp. This effect leads to a decrease in prostate enlargement, improved urinary flow, and a reduction in symptoms associated with benign prostatic hyperplasia. Clinical benefits may take several months of continuous treatment to fully manifest.

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Mechanism of action

By blocking 5α-reductase, finasteride (Propecia) prevents the conversion of testosterone into DHT.

• Serum DHT levels are reduced by approximately 65–70%.

• In the prostate, DHT reduction can reach85–90%, where type II isoenzyme predominates.

Unlike dutasteride, which inhibits all 5α-reductase isoenzymes and reduces DHT by more than 99%, finasteride does not significantly block the type I isoenzyme. For this reason, DHT production is not completely suppressed.

In the scalp, the reduction in DHT decreases androgenic activity on the hair follicles, slowing down hair miniaturization. In the prostate, finasteride reduces the volume of the gland and the risk of prostate hypertrophy progression.

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Purposes of use

Benign prostatic hypertrophy

Finasteride is widely used in the treatment of enlarged prostate. It improves urinary flow and reduces symptoms such as difficulty and pain during urination. Compared to alpha-blockers (e.g., tamsulosin), the effect is slower but longer lasting. Long-term studies have shown a significant reduction in the risk of acute urinary retention and surgery.

Hair loss (androgenetic alopecia)

Propecia is indicated for the treatment of hair loss in men. It does not completely restore hair, but slows down the progression of hair loss and can improve hair density by about 30% after six months of treatment. The effect is maintained only with continued use of the drug.

Excessive hair growth (hirsutism)

Finasteride has also been shown to be effective in treating hirsutism, significantly reducing hair growth in women with hyperandrogenism, although this use is less common.

Transgender hormone therapy

Finasteride is sometimes used as an antiandrogenic support in hormone therapy for transgender women, in combination with estrogen.

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Application in sports

In sports, finasteride is sometimes used to limit androgenic side effects related to excessive conversion of testosterone to DHT, such as acne, hair loss, and prostate hypertrophy. However, combined use with certain steroids (e.g., nandrolone) may increase the risk of androgenic side effects, as it blocks conversion to less active metabolites.

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Main effects

• treatment of benign prostatic hypertrophy

• slowing down of androgenetic alopecia

• reduction in DHT levels

• treatment of excessive hair growth

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Side effects

• decreased libido

• decrease in ejaculate volume

• gynecomastia

• possible allergic reactions (skin rash, angioedema)