A 30-year-old woman with androgenetic alopecia has a Ludwig grade II pattern. Treatment with 5% minoxidil topical solution shows partial response. She inquires about oral finasteride. Which enzyme does finasteride inhibit, and what is its specific isoenzyme selectivity?

• A 5α-reductase type 1 (expressed in sebaceous glands and scalp skin)
• B Aromatase (CYP19A1) in scalp follicles
• C Androgen receptor directly in the follicle
• D 5α-reductase type 2 (expressed predominantly in hair follicle inner root sheath) ✓

Explanation

Finasteride (1mg/day for AGA) selectively inhibits 5α-reductase type 2, which converts testosterone to dihydrotestosterone (DHT) in hair follicles, prostate, and genital skin. DHT binds follicular androgen receptors causing miniaturization of susceptible follicles. Dutasteride inhibits both type 1 and type 2 isoenzymes and is more effective. In women, finasteride must be combined with oral contraceptives (teratogenic for male fetuses). For female AGA, spironolactone (anti-androgen) is preferred in fertile women.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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