Subcutaneous Testosterone Is Effective and Safe as Gender-Affirming Hormone Therapy in Transmasculine and Gender-Diverse Adolescents and Young Adults: A Single Center's 8-Year Experience

Purpose: To describe our Center's 8-year experience with subcutaneous testosterone (SC-T) as gender-affirming hormone therapy (GAHT) in transmasculine and gender-diverse (TM/GD) youth. Methods: An Institutional Review Board (IRB)-approved retrospective study for 119 TM/GD subjects who started SC-T at age 13–19 and received SC-T for >6 months between 2012 and 2020. Results: SC-T was typically started at 25–50 mg biweekly and dose was escalated at provider's discretion. Over 96% of subjects were on 100–320 mg monthly (divided weekly or biweekly) at last follow-up. There was an overall increase in mean total and free testosterone (T) over the dose range (p=0.003), with mean total and free T levels of 460 ng/dL and 92 pg/mL, respectively, at a monthly SC-T dose of 200 mg. For subjects on SC-T without additional menstrual suppression, 54% had cessation of menses at 140 mg monthly and 97% at 200 mg monthly. On average, menses stopped 4.7 (standard deviation 3.0) months after starting SC-T. There was a decrease in high-density lipoprotein and increase in hematocrit from baseline to follow-up. Body mass index Z-scores did not change significantly with treatment. Mild acne was common; severe acne and significant injection site reactions were uncommon. Sustained hypertension, transaminitis, and dyslipidemia were infrequent. Conclusions: SC-T is well tolerated and effective in reaching recommended T levels and stopping menses in TM/GD youth. Occurrence of serious adverse effects is low and inability to tolerate injections is very uncommon. SC-T is a safe and effective alternative to intramuscular testosterone in initiation and maintenance of GAHT in TM/GD youth.