Changes in temperature perception in transgender persons undergoing gender-affirming hormone therapy

Temperature perception differs between the two biological sexes male and female with lower thermal detection thresholds found in women compared to men. However, underlying mechanisms of these differences and the influences of sex hormones are not yet sufficiently understood. To assess the effects of sex hormones on temperature perception, we measured temperature detection and pain thresholds with quantitative sensory testing and subjective temperature sensation in transgender patients undergoing gender-affirming hormone therapy (GAHT). We included 12 trans women (male-to-female transgender) and 17 trans men (female-to-male transgender) before and 3 and 6 months after start of GAHT. As a control group, we also measured 13 cis women and 10 cis men without hormone treatment at the same timepoints. Temperature detection thresholds in persons assigned female at birth at baseline were lower than in persons assigned male at birth. Accordingly, in trans women, temperature detection thresholds improved with feminizing GAHT. Pain detection thresholds did not differ between assigned sexes at birth and did not change with time. In a group of trans women undergoing GAHT with estrogen and cyproteroneacetate, for the first time we could show that the ability to detect changes in temperature detection improved, which is in congruence with a higher temperature sensitivity of women compared to men. Future studies need to assess at which neurobiological processing stages the relevant changes occur and what molecular mechanisms play a role.