Self-administration of gender-affirming hormones and supratherapeutic dosing are relatively common in Japanese transgender women.

Aim: This study was performed to determine the proportion of transgender women with self-adjusted hormone administration and excess dosing.

Methods: The medical records of 87 transgender women who visited our gender clinic from 2010 through 2019 were reviewed. The complete blood count and serum concentrations of D-dimer, gonadotropins, and sex steroids were compared between transgender women who were self-administering gender-affirming hormones and women not using such hormones.

Results: Fifty-eight of 87 (66.7%) transgender women had contravened the guideline and self-adjusted their hormone administration. The hormonal data of one woman with hypopituitarism were eliminated from the analyses. The serum gonadotropin and testosterone levels were significantly lower in the self-administration group than in the hormone-naïve group. Gonadotropin levels below the lower limit of normal were found in 32/86 (37.2%) transgender women. The testosterone levels in six transgender women were not analyzed because these women had undergone sex reassignment surgery before visiting our hospital. Testosterone levels below the lower limit of normal men were found in 36/80 (45.0%) transgender women. Unexpectedly, 29/36 (80.6%) transgender women who were classified as having suppressed serum testosterone levels had testosterone levels of <0.6 ng/mL, which corresponds to the levels in cisgender women. The white blood cell count and hemoglobin concentration were significantly different between the groups.

Conclusion: Self-initiated hormonal treatments seem to affect the serum concentrations of gonadotropin and sex steroids and the complete blood count. The prevalence of transgender women with self-adjusted use of gender-affirming hormones is high, and an excess dose of hormones occasionally occurs.