Female Pattern Baldness and Hair Loss Causes
The cause of FPHL is unknown, but it is felt to be multifactorial. Genetics probably plays a large role in the condition. The inheritance pattern may be autosomal dominant or polygenic. Many patients with FPHL have a family history of baldness in first degree male relatives. It may be harder to obtain a family history of female relatives with thinning, possibly because many women are able to hide mild to moderate thinning as women do not become obviously bald like men do. The role of hormones in the pathogenesis of FPHL has not been completely worked out. It is known that women with hyperandrogenism may develop FPHL in addition to acne, hirsuitism, and virilization. However, the vast majority of women with FPHL (98%) do not have elevated androgen levels.
In the past it was postulated that FPHL was simply the female counterpart of male androgenetic alopecia. Women with the condition were felt to have increased numbers of androgen receptors on hair follicles or possibly increased follicular sensitivity to low levels of circulating androgens. While this may be true, the lack of efficacy of finasteride (a 5 a reductase inhibitor) in treating FPHL in the one placebo-controlled, blinded study published to date, suggests that androgens may play only a partial role in the pathogenesis of some patients with FPHL and possibly no role in other patients.
It is known that FPHL results from progressive miniaturization of follicles. Large follicles producing terminal hairs are transformed into smaller vellus-like follicles producing vellus hairs. Scalp biopsies of patients with FPHL demonstrate this phenomenon by showing a range of hair shaft diameters with progressively smaller than normal shafts. Total hair density is normal (or slightly decreased in long-standing cases).