In both male and female hair thinning, there is an increase in the transformation of testosterone to DHT by both Type 1 and Type 2 5-alpha reductase enzymes. However, women have only half the amount of the 5-alpha reductase enzyme in the scalp, as do men. In addition, women have increased aromatase enzyme in the scalp follicles as compared to men. This enzyme changes testosterone to the estrogen precursors estradiol and estrone. This local formation of estrogen at the follicle, along with the lower levels of 5-alpha reductase and a lower level of androgen receptor protein, may contribute to the milder hair thinning generally experienced in women.
Most women never become totally bald.
The gene or genes for androgenetic alopecia are autosomal dominant. Autosomal dominant genes can be inherited from either side of the family or from both sides and have variable penetrance of gene expression. That is, one might inherit androgenetic alopecia from either mother or father. Hair loss can also suddenly find expression without any detectable family history. Affected members of the same family may have varying degrees of hair thinning, because other genetic factors may play a role in the expression of ones hair loss while not affecting his or her siblings.