Overview
Androgenetic alopecia — commonly called male-pattern hair loss — is a common condition that becomes more likely with age. It is driven primarily by genetics and the androgen hormone dihydrotestosterone (DHT), which miniaturizes hair follicles over time.
The role of DHT
Testosterone is converted to DHT by the enzyme 5-alpha reductase. In genetically susceptible follicles, DHT binds to androgen receptors and shortens the growth (anagen) phase, producing progressively thinner, shorter hairs until the follicle ceases visible production entirely.
The Norwood scale
Clinicians use the Hamilton–Norwood scale (types I–VII) to classify the pattern and severity of hair loss. Early stages (II–III) typically show recession at the temples; later stages (V–VII) involve extensive loss across the crown and frontal scalp.
Risk factors
Family history on either the maternal or paternal side is the strongest predictor. Age, certain medical conditions, stress, and nutritional deficiencies can accelerate or unmask thinning, but genetics remain the primary determinant.
When to consider treatment
Earlier intervention generally yields better outcomes because it is easier to maintain existing hair than to regrow hair from dormant follicles. If you notice progressive thinning — especially before age 35 — a consultation with a licensed clinician can help determine whether treatment is appropriate.