PURPOSE Intramuscular (IM) testosterone is the most common modality for testosterone therapy of both male hypogonadism and female-to-male (FTM) gender transition. However, IM injections can be painful and often are not self-administered by the patient. The objective of this study was to further characterize subcutaneous (SC) administration of testosterone as an effective and safe alternative to IM injections by evaluating the pharmacodynamics of serum total and free testosterone concentrations between weekly testosterone injections. METHODS Eleven FTM transgender patients already receiving weekly SC testosterone cypionate with documented therapeutic levels prior to enrollment had free and total serum testosterone levels measured at eight different time points during a 1-week dosing interval. RESULTS Mean levels of total and free testosterone were stable and remained well within the normal range between injections. Overall mean ± standard deviation levels for the seven samples taken between injections were 627 ± 206 ng/dL (range, 205 to 1410) for total testosterone and 146 ± 51 pg/mL (range, 38 to 348) for free testosterone. No adverse effects were encountered. CONCLUSIONS The results of this study support use of SC testosterone to achieve therapeutic and stable serum testosterone levels for the purpose of gender transition. It is anticipated that these results can be extended to hypogonadal men. This route may be preferred over IM testosterone because it is relatively painless and easy to self-inject thus allowing for the convenience and economy of patient self-administration.

中文翻译：

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在接受皮下睾酮治疗的患者中，血清睾酮浓度在两次注射之间保持稳定。

目的 肌肉注射 (IM) 睾酮是男性性腺功能减退症和女性到男性 (FTM) 性别转变的睾酮治疗最常见的方式。然而，肌肉注射可能会很痛苦，并且通常不是由患者自行给药。本研究的目的是通过评估每周睾酮注射之间血清总睾酮浓度和游离睾酮浓度的药效学，进一步确定睾酮皮下 (SC) 给药作为 IM 注射的有效和安全替代方案。方法 11 名 FTM 跨性别患者在 1 周给药间隔期间已在 8 个不同时间点测量了在 1 周给药间隔期间已接受每周一次 SC 环戊丙酸睾酮治疗并记录治疗水平的 11 名 FTM 跨性别患者。结果 总睾酮和游离睾酮的平均水平是稳定的，并且在两次注射之间保持在正常范围内。在两次注射之间采集的七个样品的总体平均值 ± 标准偏差水平为：总睾酮为 627 ± 206 ng/dL（范围，205 至 1410），游离睾酮为 146 ± 51 pg/mL（范围，38 至 348）。没有遇到任何不利影响。结论 本研究结果支持使用 SC 睾酮来达到治疗性和稳定的血清睾酮水平，以达到性别转变的目的。预计这些结果可以扩展到性腺机能减退的男性。这种途径可能优于 IM 睾酮，因为它相对无痛且易于自我注射，从而使患者自我给药的便利性和经济性成为可能。