Genetic hair loss in women: Is it the same as in men?
I'm not asked this question very often by patients, but it's a question that I think about nearly every day. Genetic hair loss in women is not the same as genetic hair loss in men. In fact, most hair specialists, including myself, steer away from using the term "androgenetic alopecia" for women and use the term "female pattern hair loss (FPHL) instead.
FPHL vs male AGA: A few of the important differences:
1. In men, androgen hormones are essential in driving the process of baldness. Without androgens there is no baldness. This is not quite so clear cut in women and blocking androgen hormones doesn't always have a benefit. In fact, increasing androgen hormones may actually help some women.
2. The genetics of hair loss in women is more complicated as well. A proportion of women develop genetic hair loss without strong family histories
3. Alterations in estrogen signalling may have an important role in FPHL.
4. In men with AGA, the drug finasteride seems to be more effective in those men with specific findings in the androgen receptor gene (i.e. shorter CAG repeats of the AR gene). In women with FPHL, the efficacy of finasteride can’t be predicted with the same degree of certainty.
5. The patterns of hair loss are different as well with women losing hair in the central scalp and men losing hair in the temples and crown.
6. A much lower proportion of women are good candidates for hair transplant surgery on account of genetic hair loss affecting the donor area.
7. Females have 3 to 3.5 times less 5 alpha reductase than men
8. Female have higher aromatase levels than men. This enzyme converts testosterone to estradiol and estrone which reduces the conversion to DHT. The levels of aromatase are 6 times higher in the frontal hairlines of women than men. These differences in aromatase may explain why retention of the frontal hairline is a typical feature of FPHL but not male balding
9. Furthermore, even though androgen receptor levels are greater in the frontal scalp than the occipital scalp in both men and women, the total receptor level is 40 % less in women.
10. The above points 7-9 may explain why the oral medication finasteride does not help as many women as it does men.
It's a mistake to think of FPHL as simply the female equivalent of male balding.
Sawaya et al J Inv Dermatol 1997; 109: 296-300