Female pattern hair loss may be triggered by low oestrogen to androgen ratio.

OBJECTIVE

In both sexes the androgenetic alopecia is known to be mediated by the conversion of circulating androgens into dihydrotestosterone within the hair follicle. However, there are a number of differences between male and female pattern baldness with estrogen known to be protective against hair loss in women. Since androgen levels in women with female pattern hair loss are mostly within the normal range, we decided to calculate the ratio of estrogens to androgens in order to find a putative trigger for their hair loss.

METHODS

We studied 20 premenopausal women with female pattern hair loss and 9 healthy women for serum levels of LH, FSH, estradiol, free and total testosterone, sex hormone binding globulin (SHBG) and dehydroepiandrosterone sulfate (DHEAS) on the first day of their menstrual cycle.

RESULTS

Although the absolute levels of androgens were normal in both groups, the ratio of estradiol to free testosterone and the ratio of estradiol to DHEAS were significantly lower in patients than in the control group.

CONCLUSIONS

We put up a hypothesis that in the presence of a genetic susceptibility, it is the estrogen to androgen ratio, as represented by the ratio of estradiol to free testosterone that might be responsible for triggering female pattern hair loss in women.