Glossary

Androgenetic alopecia (Androgenetic alopecia (AGA))

Pattern hair loss driven by DHT acting on genetically susceptible follicles. The most common cause of hair loss in both men and women.

Also: AGA, pattern hair loss, male pattern hair loss, female pattern hair loss

Androgenetic alopecia (AGA) is the umbrella diagnosis for DHT-driven pattern hair loss. It is the most common cause of hair loss in both men and women, affecting an estimated 50% of men by age 50 and a third of women by age 70.

In men, AGA presents as bitemporal recession, crown thinning, and eventual bridging of the two zones. The Norwood scale (1 to 7) is the visual classification.

In women, AGA presents as diffuse central thinning with the frontal hairline preserved (the “Christmas tree” pattern). The Ludwig (I to III) and Sinclair (1 to 5) scales are the visual classifications. Female pattern hair loss is sometimes treated as a distinct entity from male AGA because the workup, treatment options, and pacing differ.

First-line treatments with the strongest evidence: topical 5% minoxidil (women and men), oral finasteride (men), low-dose oral minoxidil (women and men), and dutasteride (men, off-label for AGA in most countries). Combination therapy outperforms monotherapy.