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, despite being relevant to counseling and surgical planning for facial gender-affirming surgery. The authors 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 to 29 years; body mass index, 18.5 to 24.9) treated with feminizing hormone therapy for less than 2 years versus 2 years or longer. Patients with previous surgical or nonsurgical facial soft-tissue interventions were excluded. Multivariable linear regressions evaluated the contribution of hormone therapy duration to malar and temporal fat volumes. Results: A total of 45 patients were included, 30 (66.7%) treated with feminizing hormone therapy for 2 years or longer and 15 (33.3%) treated for less than 2 years (median [interquartile range], 44.5 [33.5 to 65.6] versus 15.0 [11.0 to 18.0] months; P < 0.001). Patients treated with hormone therapy for 2 years or longer demonstrated a 1.6-fold greater malar fat volume (5.5 [4.2 to 6.3] versus 3.4 [2.3 to 4.2] cm 3 ; P < 0.001) and 1.4-fold greater temporal fat volume (2.8 [2.4 to 3.6] cm 3 versus 2.0 [1.7 to 2.4] cm 3 ; P = 0.01) compared with those treated for less than 2 years. When accounting for other contributory variables, such as body mass index, skull size, and total soft-tissue depth, in multivariable linear regression models, hormone therapy duration of 2 years or longer independently predicted higher malar (β = 0.51, P < 0.001) and temporal (β = 0.32, P = 0.02) fat volumes. Conclusion: 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. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.