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Subcutaneous testosterone offers alternative to intramuscular injections in transgender men
Transgender men initiating testosterone therapy via subcutaneous abdominal injections did not experience any change in free and total serum testosterone levels when compared with levels measured during previous intramuscular testosterone injections, study data show.
“Recent reports indicate that [subcutaneous] administration of testosterone esters may be an acceptable alternative to [intramuscular] injections in hypogonadal men and [female-to-male] transgender patients,” Julie McFarland, MD, of the department of obstetrics and gynecology at Maine Medical Center in Portland, and colleagues wrote. “Genetic females undergoing gender transition provide an ideal opportunity to assess pharmacokinetics because their low endogenous secretion of testosterone contributes minimally to serum measurements of testosterone. Providing information regarding the pharmacokinetics of testosterone ester injections will further characterize its efficacy and reliability as well as provide information regarding appropriate timing of serum sampling to monitor therapy.”
McFarland and colleagues analyzed data from 11 healthy transgender men already receiving testosterone therapy with testosterone cypionate (Hikma Farmaceutica) for at least 2 months, recruited from the Maine Medical Center (mean age, 31 years; mean BMI, 28.5 kg/m²; mean duration of testosterone therapy, 119 weeks). Participants had free and total testosterone concentrations in the normal adult male range at baseline. All patients self-administered testosterone cypionate into abdominal subcutaneous tissue; blood samples were collected at baseline and 6 hours and at 1, 2, 3, 4, 5 and 7 days after injection to measure free and total serum testosterone. Researchers also evaluated efficacy (as measured by suppression of menses and serum estradiol, as well as appearance of facial hair and deepening of voice) and safety.
Researchers found that mean levels of total and free testosterone were stable and remained within normal range between injections; mean levels for the seven samples taken between injections were 627 ng/dL for total testosterone and 146 pg/mL for free testosterone. There was a correlation observed between mean serum total testosterone and subcutaneous testosterone dose (P = .006). In a regression model that included BMI, only total testosterone was a significant independent predictor of serum meal total testosterone (P = .005), explaining 58.9% of the variance in mean serum total testosterone, according to researchers.
“Near identical serum concentrations of total and free testosterone 7 days apart just prior to injections further supports consistency of serum testosterone levels with [subcutaneous] injections,” the researchers wrote. “The patients with testosterone levels within the lower half of the normal range were all receiving relatively small doses of testosterone. Thus, increasing the dose of testosterone would reasonably be anticipated to maintain serum testosterone levels well within the normal range throughout the week between injections. Our data indicate that the dose can be monitored by a single serum total testosterone measurement 1 to 5 days after an injection.”
All participants developed amenorrhea and reported deepening of the voice and development of facial hair. There were no local reactions to injections reported and no reports of decline in energy, well-being or mood in the 2 days prior to injection. – by Regina Schaffer
Disclosures: The authors report no relevant financial disclosures.