Hair loss in men.

Mechanism: the hormone dihydrotestosterone (DHT) shortens the growth phase in genetically sensitive hair follicles. Each new hair becomes thinner and shorter until the follicle only produces fuzz. Affected are the forehead (temples) and the crown; the rim remains because its follicles are DHT-insensitive. Around two thirds of men are affected by 50.

Stages: the Hamilton-Norwood scale describes seven stages from mild temple recession to the horseshoe rim. It helps to estimate progression and decide whether and how to treat.

What the evidence supports: (1) finasteride 1 mg daily (prescription) blocks DHT formation and stops loss in about 80–90 %; possible sexual side effects are rare but must be discussed. (2) Minoxidil 5 % topical extends the growth phase. (3) Both together are standard. Anyone who stops loses the effect within a year.

PRP: as a supplement in early to middle stages: more density, thicker hairs in studies; three to four sessions, then six-monthly maintenance. No replacement for finasteride/minoxidil, but an option for men who do not want medication – with a smaller effect.

Transplant: sensible with a stable course (usually from the mid-30s, under ongoing therapy), sufficient donor hair and realistic expectations. It moves hair, it does not stop loss – without medication the surroundings keep thinning.

Not proven: caffeine shampoos, biotin without deficiency, laser combs with weak evidence, 'hair growth vitamins'. And an honest option: a short cut or a shave. Many men who choose that do not regret it.