Introduction to Androgenetic Alopecia
It refers to loss of hair seen with increasing age in genetically predisposed individuals. Since physiological amounts of circulating androgens are needed to express this genetic trait it is called androgenetic alopecia.
Fewer predisposing genes are needed for expression of AGA in men (whose androgen levels are physiologically high) than in women whose levels are much lower. This explains why a family history of AGA in mother is usually a bad prognostic factor.
Pathology- Hair follicles are not reduced in number in early stages, but there is significant reduction in their density & size later with accompanying decreases in shaft thickness. Biopsy of affected scalp reveals a higher proportion of telogen follicles
Varying diameters & depths of follicles signify the transformation of terminal to vellus types. There is gradual & progressive miniaturization of hair of the affected areas.
The affected follicles have a progressively shorter anagen phase & become smaller & superficial, producing hairs that are shorter, thinner & lighter in colour.