Similar to male pattern baldness, female pattern baldness is caused by normally present male hormone (yes, that's right, male hormone) or Androgen. Male hormone slowly kills the Androgen sensitive follicles within the balding pattern in a similar, but not identical way that it does in men. This, as with men, results in progressive miniaturization of the hair follicle and shortening of the growth phase. (For details, go to Hair Loss Explained.)

Since females carry the same genes for baldness as their father, brothers, uncles, etc., you may be wondering why women don't bald nearly as frequently or with the same severity as men. The reason is that females produce only a tiny amount of Androgen or male hormone. The women who do bald typically have an unusual "sensitivity" to the very small levels of male hormone normally present in females. Female pattern baldness is therefore not caused by an excess of male hormone, but rather by an unusual "Androgen sensitivity".

The balding pattern seen in women is therefore different than that seen in men, being more oval and preserving the hairline area. The classification of female pattern hair loss by Ludwig is shown below.

Very rarely, a woman may develop abnormally high levels of male hormone (from a disease process). These women will in fact have a male pattern of hair loss similar to their father, brothers, uncles, etc.