Clinical and phototrichogrammatic evaluation of estradiol replacement therapy on hair growth in postmenopausal Japanese women with female pattern hair loss: a pilot study

Female pattern hair loss (FPHL) is known to present with characteristic pathological conditions, including reduced overall hair density. Female hormones affect hair condition; however, the detailed mechanism is unknown. Furthermore, research on the topic is complicated by the fact that senescent alopecia often occurs concurrently with FPHL. Therefore, we investigated the effect of estradiol, a female hormone, on hair growth by eliminating aging factors and objectively evaluating hair changes caused by female hormone replacement therapy (HRT). This study was conducted to elucidate the mechanism through which female hormones exert their effects on hair. The study included 11 female patients undergoing HRT who were evaluated before initiating HRT, 3 months after initiating HRT, and 6 months after initiating HRT. The thinning hair score, hair density, telogen hair rate, telogen plucking strength, hair growth rate, and hair thickness were measured and evaluated. Furthermore, hematological tests were performed to assess the general physical condition of the participants. HRT increased the telogen hair rate ( = .010, paired test) at 3 months, improved frontal hairline thinning score ( = .008, Wilcoxon test), and increased the plucking strength ( = .013, paired test) at 6 months. The limitation of this study included the relatively small sample size, inability to conduct further long-term tests because of participant burden, and lack of a control group. The results suggested that HRT improved the appearance of the frontal hairline. As few studies have analyzed the effects of female hormones on human hair, a novel finding of this study was the effects of estradiol on the plucking strength after excluding age as a factor. We believe that these findings will contribute to understanding FPHL and developing female hormone-related treatments.