Androgenetic alopecia (male and female pattern hair loss)

Key takeaways

• It is very common and mostly inherited. The European S3 guideline puts lifetime frequency at up to 80% of white men and 42% of women (Kanti 2018), and a 2025 Canadian consensus says 40 to 50% of men and women are affected by age 50 (Landells 2025). Figures vary by ancestry and study.
• The core change is miniaturization, not sudden shedding. Susceptible follicles make progressively shorter, thinner hairs until they look like fine vellus hair. Frontal, mid-scalp and crown follicles are vulnerable; the back and sides are spared, which is why transplants work (Liu 2025).
• Genetics is polygenic, not "your mother's father". Genome-wide studies have found more than 380 associated loci (Liu 2025), and polygenic scores built on European data predict poorly in African men (AUC 0.513 to 0.546, barely above chance) (Janivara 2025).
• For men the best-proven options are oral finasteride and topical minoxidil. Finasteride 1 mg/day in two 1-year trials (1,553 men) added 107 hairs over placebo at 1 year and 138 at 2 years in a 5.1 cm2 vertex circle, while placebo men kept losing hair (Kaufman 1998). A meta-analysis of 12 trials (3,927 men) found a number needed to treat of 5.6 at 1 year and 3.4 at 2 or more years for a man to see himself as improved, with a small rise in erectile dysfunction (number needed to harm about 82) (Mella 2010).
• For women, topical minoxidil has the best randomized evidence. A Cochrane review (47 trials, 5,290 women) found minoxidil 2% about doubled the chance of a moderate-to-marked regrowth rating (RR 1.93) and added about 13 hairs per cm2; finasteride 1 mg showed no benefit over placebo in three small trials (van Zuuren 2016).
• Anti-androgens in women have thinner evidence than people assume. In 48 premenopausal women, spironolactone 100 mg on top of 3% minoxidil raised terminal hair count by 9.5 vs 5.3 hairs per cm2 over 24 weeks, which was not statistically significant, and 37.5% had menstrual irregularity (Werachattawatchai 2025). A 204-woman trial found bicalutamide 50 mg slightly ahead of spironolactone 100 mg on trichoscopy but not on clinical endpoints (Jha 2026). Both are off-label and unsafe in pregnancy.
• Treatments only work while you use them. Placebo arms show ongoing loss, and stopping an effective drug lets the process resume.
• It affects wellbeing: a meta-analysis of 41 studies (7,995 people) found moderate impairment in quality of life and emotions but no pooled link with clinical depression (Huang 2021).
• Pattern loss can travel with metabolic risk. A meta-analysis of 19 studies found about 3.5 times the odds of metabolic syndrome in people with AGA, but this is an association, not proof of cause (Qiu 2022).

How it works and what it looks like

In men the process is driven by androgen signalling in vulnerable follicles, which shortens the growth phase with each cycle. In women the molecular basis is less clear and oestrogen may be protective (Liu 2025; Kearney 2026). See DHT and pattern hair loss.

• Men: temple recession and crown thinning, progressing to a horseshoe of fringe hair. The Norwood-Hamilton scale (I to VII) is standard.
• Women: diffuse thinning over the crown with a widening centre part and usually a preserved frontal hairline (Ludwig I to III). See hair loss scales.
• Onset is usually after puberty in men and after menopause in women, though younger people can be affected.

Diagnosis rests on the pattern, family history, a pull test and measured differences in hair width. Look-alikes in women include chronic telogen effluvium, diffuse alopecia areata and scarring alopecias, so clinicians check iron, thyroid and signs of androgen excess (Kearney 2026). See telogen effluvium, alopecia areata, PCOS and hair and thyroid and hair.

What the studies show about treatments

Doses are as studied.

The Canadian consensus (11 physicians, 45 interventions, partly industry-affiliated) recommended seven interventions: oral dutasteride, oral finasteride, topical finasteride, topical minoxidil, PRP, microneedling and oral minoxidil. It rejected 17, including caffeine, rosemary oil and adenosine (Landells 2025). The European S3 guideline is the main evidence-based guideline but has expired (Kanti 2018).

What is coming: a 2026 review lists topical anti-androgens such as clascoterone and GT20029, prolactin-receptor biologics and extended-release minoxidil, all investigational for hair (Agrawal 2026). See the treatment ladder for the ranked order.

Hair type notes

• Women who might become pregnant need effective contraception on anti-androgens. Finasteride, dutasteride and spironolactone are unsafe in pregnancy.
• In Black women, rule out traction and central centrifugal scarring causes before assuming pattern loss (see CCCA and traction alopecia).
• Tight curl can hide early thinning in photos; fine, low-density hair shows loss sooner. None of this changes which treatments work.
• A flaky or inflamed scalp needs diagnosis first, because inflammation can cause shedding that looks like pattern loss.

Bottom line

Start early, because treatment keeps hair more than it regrows it, and photograph the same areas monthly under the same light. Topical minoxidil is the first-line option for both sexes; oral finasteride is the best-proven drug for men. Give treatment 6 to 12 months, and expect an early shed after starting minoxidil. See a dermatologist if loss is sudden, patchy, itchy, painful or scarring. Prescription medicines are information, not advice. Discuss with a doctor.