Duration of Feminizing Hormone Therapy on Facial Fat Volumes.

BACKGROUND:Gender-affirming feminizing hormone therapy induces body fat redistribution. However, the amount and timing of facial fat changes in response to feminizing hormone therapy are unknown, albeit relevant to counseling and surgical planning for facial gender-affirming surgery. In this work, we assessed the influence of feminizing hormone therapy duration on malar and temporal fat volume. METHODS:Malar and temporal fat volumes were compared using computed tomography in transfeminine patients (age 20-29 years, body mass index [BMI] 18.5-24.9) treated with feminizing hormone therapy for <2 years versus ≥2 years. Patients with prior surgical or non-surgical facial soft-tissue interventions were excluded. Multivariable linear regressions evaluated the contribution of hormone therapy duration to malar and temporal fat volumes. RESULTS:45 patients were included with 30 patients (66.7%) treated with feminizing hormone therapy for ≥2 years and 15 patients (33.3%) treated for <2 years (median[interquartile range, IQR]: 44.5[33.5-65.6] vs. 15.0[11.0-18.0] months, p<0.001). Patients treated with hormone therapy for ≥2 years demonstrated a 1.6-fold greater malar fat volume (5.5[4.2-6.3] vs. 3.4[2.3-4.2] cm 3,p<0.001) and 1.4-fold greater temporal fat volume (2.8[2.4-3.6] cm 3 vs. 2.0[1.7-2.4] cm 3, p=0.01) compared to those treated for <2 years. When accounting for other contributory variables such as BMI, skull size, and total soft-tissue depth in multivariable linear regression models, hormone therapy duration ≥2 years independently predicted higher malar (β=0.51, p<0.001) and temporal (β=0.32, p=0.02) fat volumes. CONCLUSIONS:Feminizing hormone therapy increases malar and temporal fat volumes by approximately 2 cm 3 and 0.8 cm 3 for each area, respectively, after 2 years of treatment.