Efficacy of Sex Steroid Therapy Without Progestin or GnRH Agonist for Gonadal Suppression in Adult Transgender Patients.

Context: Testosterone (T) or estradiol (E2) are administered to suppress gonadal function in female-to-male (FTM) and male-to-female (MTF) transgender patients. How often sex steroids cause adequate suppression without GnRH agonist (GnRHa) or progestin therapy has not been reported.
Objectives: (1) To determine how often T and E2 therapy alone can effectively suppress gonadal function in MTF and FTM transgender patients, and (2) to determine the frequency and range of serum E2 levels above the normal male range in FTM patients receiving T therapy.
Design: Retrospective cohort study.
Setting: Outpatient reproductive endocrinology clinic at an academic medical center.
Patients: A total of 65 FTM and 33 MTF patients were included who were > 18 years of age and not receiving progestin or GnRHa therapy.
Intervention: Female-to-male patients were receiving T through injections or gel. Male-to-female patients were receiving oral or subcutaneous E2.
Main Outcome Measurements: In FTM patients the indicator of ovary suppression was amenorrhea. In MTF patients, the indicator of testes suppression was T levels <50 ng/dL.
Results: Median serum total T level for FTM patients was 712 ng/dL (range, 370-1164 ng/dL). On T therapy alone, 90.8% of patients achieved amenorrhea and 49.2% of patients had serum E2 levels above the normal range for women. For MTF patients, the median serum E2 level was 129.2 pg/mL (range, 75-197 pg/mL). On E2 therapy alone, 84.8% of MTF patients had adequate suppression of testicular function.
Conclusions: Testosterone and E2 therapy are usually effective without progestin or GnRHa therapy to suppress gonadal function in transgender patients. Progestin and/or GnRHa therapy should only be initiated in those patients who do not have adequate gonadal suppression on optimized doses of T or E2 alone.
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