Endocrine Abstracts

Background: Gender-affirming hormone therapy in transgender persons induces secondary characteristics of the experienced gender. However, androgens and estrogens are also thought to be involved in insulin sensitivity and research suggests a dose-dependent risk for developing insulin resistance when administrated in supraphysiological doses.

Aims: To assess the influence of gender-affirming hormone therapy on glucose metabolism in transgender persons.

Methods: In 90 transgender persons (35 transgender men and 55 transgender women) an OGTT was performed at baseline and one year after the introduction of gender-affirming hormone therapy as part of the ENIGI study (European Network for the Investigation of Gender Incongruence). HOMA-IR and AUC glucose during OGTT were used to quantify insulin resistance (IR).

Results: AUC glucose did not change significantly in either sex. In transgender women, we observed an increase in the median-calculated HOMA-IR, from 1.58 [1.08–1.97] to 2.06 [1.49–2.76] (P<0.001) indicating higher IR after administration of estrogens and anti-androgens, an increase in total fat percentage from 18.60%±5.3 to 24.50%±10.11 (P<0.001), and a decrease in the waist-to-hip ratio (WHR) from 0.87±0.068 to 0.84±0.084 (P=0.001). In transgender men, there was no significant difference in the median-calculated HOMA-IR, but we observed a decrease in total fat percentage from 28.49%±5.92 at baseline to 24.30%±7.17 after one year (P<0.001) and an increase in total activity score from 7.30±2.56 to 9.05±2.46 (P<0.001). In transgender women, we observed a positive correlation (R=0.273, P=0.045) between change in WHR and change in HOMA-IR and a positive correlation (Rs=0.287, P=0.034) between change in HOMA-IR and change in cholesterol. In trans men, these correlations were not significant.

Conclusions: This study has identified significant changes in glucose metabolism in transgender women after one year of gender-affirming hormone therapy; IR increased, which is in line with the observed change in body composition. In transgender men, no change in IR was proven, despite a decrease in fat percentage and an increase in total activity scores.