Estrogen hormone therapy stabilizes lateral hairline in transfeminine patients: Implications for facial feminization surgery.

BACKGROUND: Although several studies report on the suppressing effects of estrogen therapy on facial and body hair in transgender and nonbinary (TGNB) individuals, few studies have elucidated its effects on hairline stability on the scalp. In this study, we assessed the influence of estrogen therapy on forehead length. METHODS: All TGNB patients, aged 30 years or older, assigned male at birth (AMAB) seeking facial feminization surgery were included in the study. Central and forehead lengths were collected at the initial consultation visits. Variables, including age, duration of hormone replacement therapy (HRT), presence of spironolactone, and presence of other hair treatments, such as finasteride, dutasteride, or minoxidil, that potentially influence hair growth were collected by chart review. Multivariable linear regressions were constructed with relevant predictor variables while also incorporating global health scores as a proxy for psychological effects on hair loss. RESULTS: Overall, 171 patients were included in this study, with a median age of 36.0 (interquartile range (IQR) 32.0-46.0) years and median HRT duration of 2.0 (IQR 1.0-6.0) years. Multivariable linear regressions revealed no significant predictors for central forehead length. However, lateral forehead length was positively predicted by age (B=0.06, 95% confidence interval (CI) [0.03-0.08], p < 0.001) and hair treatment (B=0.66, 95% CI [0.14-1.18], p = 0.01), but negatively predicted by HRT duration (B=-0.07, 95% CI [-0.10 to -0.04], p < 0.001). CONCLUSIONS: Although older age is a predictor of lateral hairline recession in TGNB AMAB individuals, lateral forehead length was also predicted to decrease by 0.07 cm with each year of feminizing hormone therapy in patients over 30 years of age.