Retinoids putting the "a" in alopecia.

Vitamin A (vitA) has many roles in human biology. With respect to hair, knockout mice for vitA receptor, hairless, and vitamin D genes have similar phenotypes, and follicle loss occurs during catagen. Hypovitaminosis A from inadequate vitA intake causes hair loss. This work suggests that dietary vitA may have a role in precipitating and maintaining alopecias as well.