"Miniaturization" and "Anisotrichosis" in Androgenetic Alopecia

Terms in AGA: Miniaturization and Anisotrichosis

Androgenetic alopecia is common in men and women. By 50 years, about 50 % of men and 30 % of women have some evidence of androgenetic alopecia. The early features of AGA include hair shedding in some and hair loss in specific areas (temples and crown in men and central scalp in women).

When examined up close as in this photo, one can see "miniaturization" of hairs whereby some thicker hairs undergo a change to thinner hairs. Most hairs we have on our scalp as teenagers range in around 70-90 micrometers in diameter. During the process of androgenetic alopecia, the follicles become thinner and thinner and over time reduce slowly to 50 micrometers then 20 then 10 etc. Finally the fibers are so thin and short that they fail to reemerge from the scalp.

Not all hairs become thin and not all hairs thin at the same speed (rate). There is great variation in the thickness of hairs. We call this variation in hair shaft thickness "anisotrichosis." Two finding of miniaturization and anisotrichosis is a typical feature of androgenetic alopecia in both men and women.