Three-dimensional facial volumetric changes in transgender individuals induced by gender-affirming hormone therapy: a stereophotogrammetric assessment.

Gender had a significant global multivariate effect on the combined set of facial volumes at all time points in transgender individuals undergoing GAHT.

• A multivariate analysis of covariance (MANCOVA) was conducted with facial volumetric regions as dependent variables, followed by post-hoc univariate ANCOVA.
• The global multivariate effect of gender on combined facial volumes was significant at all time points (p < 0.001).
• The study enrolled 30 participants: 17 transgender men, 1 non-binary transmasculine individual, and 13 transgender women.
• Facial scans were obtained at four time points: baseline (T0), 3 months (T1), 6 months (T2), and 12 months (T3) after initiation of GAHT.

Trans men showed a consistent and significant increase in total facial volume and in all five facial regions over the 12-month observation period.

• Increases were observed in all five regions analyzed: mandibular, maxillary, frontal, mental (chin), and labial.
• The most notable increases were observed between T0 and T1 (baseline to 3 months), and changes were sustained through T3 (12 months).
• The pattern of change was described as 'rapid and homogeneous,' particularly pronounced in the lower third of the face.
• Trans men (n = 17, plus 1 non-binary transmasculine individual) were receiving testosterone as part of GAHT.

Trans women exhibited more variable and localized facial volumetric changes compared to trans men over the 12-month period.

• Trans women (n = 13) showed increases in maxillary, frontal, and labial volumes at T1 and T2.
• More widespread volume gains in four of five facial regions were observed at T3 (12 months), suggesting gradual adipose redistribution induced by estradiol.
• Trans women's changes were described as 'more subtle and regionally distributed' compared to trans men.
• Trans women received estradiol combined with an antiandrogen as part of GAHT.

The mandibular region showed the most pronounced region-specific volumetric changes among all facial regions assessed.

• Total facial and mandibular volumes were identified as having the most pronounced region-specific changes between the two groups.
• The lower third of the face showed the most notable increases in trans men.
• Five facial regions were analyzed: mandibular, maxillary, frontal, mental (chin), and labial.
• Stereophotogrammetry using the Vectra H1 device was used for volumetric assessments.

Spearman's correlation was used to assess associations between weight variation and facial volume changes across participants.

• Statistical analysis included the Mann-Whitney U test to compare groups and Spearman's correlation to assess associations between weight variation and facial volume changes.
• This was a longitudinal observational study with assessments at four time points over 12 months.
• All participants were receiving care at the Gender Diversity Gynecology Clinic (GDIG) of the Hospital das Clínicas, Ribeirão Preto Medical School, University of São Paulo (HCFMRP-USP).

GAHT was found to promote facial characteristics aligned with gender identity in transgender individuals, with distinct patterns of change between transgender men and women.

• Testosterone was associated with faster and more uniform masculinization of facial structures.
• Estrogen associated with an antiandrogen led to more subtle and regionally distributed feminization over time.
• Changes in trans women were attributed to 'gradual adipose redistribution induced by estradiol.'
• The study used stereophotogrammetry (Vectra H1) for objective, three-dimensional facial volumetric assessment across 12 months.