Androgenetic alopecia
Androgenetic alopecia is the most common cause of hair loss in both males and females. The pattern and severity of the baldness depend on both hormonal (circulating androgens) and genetic factors and vary between males and females. The condition is polygenic with variable expressivity.
Pathophysiology
- Dihydrotestosterone binds to androgen receptors on hair follicles.
- Follicular miniaturization: androgens shorten the anagen phase of hair growth → vellus hair formation (thin, short hair)
- 5α-reductase, an enzyme present in hair follicles, converts testosterone into the more potent dihydrotestosterone, which is responsible for alopecia.
Treatment
- Topical minoxidil
- Direct arterial vasodilator
- First-line treatment for men and women
- Finasteride
- 5α-reductase inhibitor
- First-line treatment for men