Serum Testosterone Concentrations Remain Stable Between Injections in Patients Receiving Subcutaneous Testosterone.
Level 4 - case-series / case-control
Prospective single-arm pharmacokinetic case series without a control group
PubMed 29264562 · doi:10.1210/js.2017-00148
What was done
Eleven female-to-male (FTM) transgender individuals already receiving weekly subcutaneous (SC) testosterone cypionate with documented therapeutic levels were evaluated. Serum total and free testosterone levels were measured at eight distinct time points across a 1-week dosing interval to assess pharmacodynamics and safety.
What was found
Mean total and free testosterone levels remained stable and within the normal physiological range throughout the dosing interval. Across the seven measurements taken between injections, mean ± standard deviation total testosterone was 627 ± 206 ng/dL (range: 205 to 1410 ng/dL) and free testosterone was 146 ± 51 pg/mL (range: 38 to 348 pg/mL). No adverse effects were reported.
Why it matters
These findings support subcutaneous administration of testosterone cypionate as an effective, stable, and easier-to-self-administer alternative to traditional intramuscular injections for gender transition and potentially male hypogonadism.
Limits
The study is limited by a very small sample size (n = 11) and the absence of a randomized or direct intramuscular comparator group. The evaluation was confined to a single 1-week interval in patients already stabilized on therapy, and generalizability to hypogonadal men was not directly tested.
Cited by
- supports Subcutaneous injection of testosterone provides slower absorption and more stable serum hormone concentrations compared to intramuscular injection.