What causes androgenetic alopecia (pattern hair loss)?
Androgenetic alopecia is driven by genetically determined sensitivity of scalp follicles to dihydrotestosterone (DHT). The follicles miniaturize over successive growth cycles, producing the recognizable patterns. Ferritin, thyroid, and nutritional status modulate but do not cause it.
Full answer
Androgenetic alopecia — the most common cause of hair loss in men and women — is driven by genetically inherited sensitivity of scalp hair follicles to dihydrotestosterone (DHT), the more potent androgen produced from testosterone by 5-alpha-reductase. In susceptible follicles, DHT progressively shortens the anagen (growth) phase and miniaturizes the follicle over successive cycles, producing the characteristic frontotemporal recession and vertex thinning in men and diffuse central thinning in women. Total testosterone level does not predict hair loss — follicle sensitivity does. Modifiable contributors that worsen the picture include low ferritin, thyroid dysfunction, severe caloric or protein restriction, post-partum and post-COVID telogen shifts, and certain medications. Provider review reads the full picture before recommending finasteride, minoxidil, or combination therapy.
Educational. Not a substitute for individualized provider review.
- Androgenetic Alopecia — Primary source · oMeds
- Reviewed by Dr. Laura Purdy, MD, MBA · Clinical Director, oMeds · Last reviewed 2026-05-29