V.H. Price, Dept. of Dermatology
University of California San Francisco, San Francisco, CA, USA
Study Information and Results:
Androgenetic alopecia (AGA) is caused by androgens in genetically susceptible women and men. The thinning, also known in women as female pattern hair loss, begins between ages 12 and 40 years. Inheritance pattern is polygenic, and incidence is the same as in men. In susceptible hair follicles, dihydrotestosterone binds to androgen receptor, and the hormone-receptor complex activates the genes responsible for the gradual transformation of large terminal follicles to miniaturized follicles.
As in young men with Androgenetic Alopecia, young women have more androgen receptors, higher levels of 5 alpha reductase and lower levels of aromatase, in frontal than in occipital follicles. However, the process is milder in women than in men because of differences in these levels. The miniaturized follicles produce shorter and finer hairs of various lengths and diameters, and these miniaturized hairs are the hallmark of the condition. In women, hair thinning is diffuse but most marked on the frontal and parietal scalp. Won typically retain a rim of hair along the frontal hairline.
Increased spacing between hairs makes the central part look wider over the frontal scalp compared to the occipital scalp. Diagnosis is supported by these features including miniaturized hairs, pattern of thinning, and early age of onset. Most women with Androgenetic Alopecia have normal menses, pregnancies.
Extensive hormonal testing is usually not needed unless symptoms and signs of androgen excess are present such as hirsutism, severe unresponsive cystic acne, virilization, or galactorrhea. Androgen excess is assessed by measurment of serum total or free testosterone, dehydroepiandrosterone sulfate, prolactin, and other causes of hair loss are ruled out by serum thyrotropin, iron and ferritin.
Topical minoxidil solution is the only drug available for promoting hair growth in women with Androgenetic Alopecia. Efficacy has been shown in double-blind studies using hair counts and hair weight. Minoxidil solution must be applied twice daily directly to a dry scalp. Women are devastated by their thinning hair and need reassurance that they may safely use hair cosmetics to make their hair appear fuller.