Localized Rhabdomyolysis Associated With Testosterone Enanthate for Gender-Affirming Hormonal Therapy

BACKGROUND/OBJECTIVE: Rhabdomyolysis is a condition characterized by the destruction of skeletal muscle tissue that leads to systemic complications. We present a case of gender-affirming intramuscular (IM) testosterone therapy precipitating localized deltoid rhabdomyolysis. CASE REPORT: A 34-year-old transgender man presented to the emergency department with dark-colored urine and pain in the left deltoid muscle where he had been injecting IM testosterone. He was found to have significant elevation in the level of creatinine kinase that was consistent with rhabdomyolysis and managed with intravenous fluids. He received trial therapy with IM testosterone again in the contralateral deltoid twice with recurrent rhabdomyolysis. He eventually transitioned to subcutaneous testosterone to achieve his masculinization goals without adverse effects. DISCUSSION: Localized anabolic steroid use has been associated with rhabdomyolysis. However, to the best of our knowledge, this is the first case report of rhabdomyolysis attributed to gender-affirming testosterone therapy. Our patient had been administering testosterone intramuscularly into larger muscles (thigh and gluteus) for many years without any issues, whereas recurrent focal rhabdomyolysis developed only in association with deltoid injections. We theorize that a relative increase in dose and volume of testosterone per gram of muscle after switching to the deltoid site precipitated rhabdomyolysis. Subcutaneous testosterone is an acceptable alternative to IM testosterone for patients desiring an injectable delivery route with minimal adverse effects. CONCLUSION: This case report highlights the potential risk of rhabdomyolysis associated with IM testosterone administration in the deltoid region for gender-affirming care. Patients on IM testosterone should use the thigh or gluteal muscles rather than the deltoid.