Subcutaneous Testosterone: An Effective Delivery Mechanism for Masculinizing Young Transgender Men

Purpose: Testosterone is the recommended treatment for transgender youth who desire the development of male secondary sexual characteristics. While intramuscular injection remains the most common means of delivering injectable testosterone, subcutaneous (SC) delivery has been used with clinical success. No data reporting serum levels and feasibility are available. We aimed to determine both if subcutaneous delivery of testosterone resulted in menstrual cessation, and the normal male ranges of serum testosterone in this subpopulation of female-to-male transgender youth. Methods: Within an urban hospital-affiliated Adolescent Medicine clinic, thirty-six youth aged 13 to 24 years transitioning from female to male received testosterone cypionate via subcutaneous injections for masculinization. Participants were a subpopulation of those enrolled in a longitudinal, prospective study examining the impact of treatment for transgender youth. A titrated dose of testosterone cypionate (average dose 46.4 mg per week) via subcutaneous injection was delivered over 6 months. The main outcomes included menstrual cessation as well as raised free and total testosterone levels. Results: Eighty-five percent of participants had ceased menstrual bleeding within 6 months after initiating testosterone. The average time to menstrual cessation was 2.9 months. Most participants (91.4%) reached total testosterone levels within the normal male range after 6 months of subcutaneous delivery (49-1138 ng/dL, 521.4 ng/dL total test). Few adverse effects were reported. Conclusion: Subcutaneous delivery of testosterone for masculinization of transgender youth seems to be effective and well tolerated over short treatment times. Additional studies are needed to determine whether long term use of subcutaneous testosterone delivery yield similar results.