Different Hairs in AGA

Terminal, Vellus and Miniaturized

We will continue our discussion of how hair follicles change during the course of androgenetic alopecia (male pattern balding and female androgenetic alopecia). In general, hair follicles become thinner during the course of genetic hair loss. Before the onset of hair loss, most hairs in the scalp are thicker "terminal" hairs. These are typically 60 to 80 micrometers in diameter.

During the thinning process, terminal hairs become "miniaturized" hairs and eventually "miniaturized" hairs become "vellus" hairs. Vellus hairs are always less than 30 micrometers in diameters. During the course of balding, terminal hairs become less common and vellus hairs become more common. During advanced balding, vellus hairs outnumber terminal hairs in the areas of balding. In such a case, we say that the terminal to vellus ratio (T:V) ratio is much less than 1:2.