Female Pattern Hair Loss Possibly Caused by Tamoxifen: Androgen Receptor Expression in the Outer Root Sheath in the Affected Area

This report presents a case of female pattern hair loss (FPHL) possibly caused by tamoxifen, a drug used in anti-estrogen therapy for hormone receptor-positive breast cancer in premenopausal women. The patient had diffuse hair loss that persisted for more than 3 years, and histopathological findings revealed hair follicle miniaturization, indicating FPHL caused by tamoxifen. Immunohistochemical analysis of androgen receptor (AR) showed increased AR expression in the outer root sheath in the affected area, suggesting that an androgen pathway induced by tamoxifen might contribute to the pathomechanism of FPHL. Further studies are necessary to evaluate the significance of increased expression of AR in the outer root sheath for a shortened anagen phase observed in the present case.