Fourteen patients met inclusion criteria and signed consent to participate. Hormone levels were compared between the two preinjection samples (7 days apart), as well as the first preinjection sample and the 6-hour sample by two-sided paired t test. Continuous data were described as mean (standard deviation) or as median (range), as appropriate; categorical data were summarized as frequencies (n, %). Safety was assessed by history and physical examination of injections sites, as well as monitoring chemistry panels and hematocrits. The lower limit of detection for total testosterone was 0.84 ng/dL and for free testosterone was 0.1 pg/mL. Interassay precision free testosterone (% buffer/serum ratio of 2.11) was 11.64%. Serum total testosterone was measured by liquid chromatography/mass spectrometry, and free testosterone was measured using equilibrium dialysis (Quest Diagnostics). Alternatively, testosterone may impact the conversion of the learned values into action selection, or the temporal dynamics of the evidence accumulation. It remains to be shown, though, which specific aspects of reward processing testosterone acts on. Besides this insight from animal research, testosterone and reward processing have also been linked in humans 19, 20. Through what neurobiological pathways could testosterone modulate such complex social behaviors? One hundred and ninety-two male participants received either a single dose of testosterone (150 mg) or a placebo and performed a prosocial and self-benefitting reinforcement learning task. Conversely, less frequent injections can cause peaks and troughs in hormone levels, potentially exacerbating mood instability. More frequent administration, such as daily injections, tends to maintain steadier testosterone plasma concentrations, reducing fluctuations that may precipitate mood swings and energy variability. Thus, the choice of injection interval involves balancing hormone stability against patient preference and injection tolerability to optimize TRT outcomes. Weekly or bi-weekly schedules, while offering improved injection comfort, often exhibit greater hormonal variability that requires careful dose titration to mitigate symptomatic oscillations. Daily injections tend to produce minimal hormone fluctuations, maintaining near steady-state testosterone concentrations that optimize receptor engagement and symptom control. Injection consistency is vital to minimize peaks and troughs in testosterone concentrations, thereby stabilizing hormone levels within the therapeutic range. When evaluating testosterone replacement therapy (TRT) protocols, the stability of serum hormone levels across different injection schedules is a critical factor influencing therapeutic efficacy and patient outcomes. The weekly protocol balances the need to sustain stable serum testosterone concentrations with the practical aspects of administration frequency. Testosterone injections introduce exogenous testosterone directly into the systemic circulation, bypassing hepatic first-pass metabolism and enabling controlled elevation of serum testosterone levels. Testosterone replacement therapy (TRT) protocols differ mainly by injection frequency—daily, weekly, or bi-weekly—impacting serum testosterone stability and side effect profiles. Contrasting with this view, the hypothesis that testosterone drives status-seeking via reputation building rather than dominance 15, 16 would predict that based on the social context, testosterone might conditionally promote prosocial and especially socially desirable behavior to build up a reputation and increase status. Exogenous testosterone alleviates subordination to the dominance of others 10,11,12 and reduces the physiological response to being evaluated by others . Research in the past decade has demonstrated that testosterone is implicated in a wide spectrum of socially dominant behaviors 8, 9. These conversions matter when you and your clinician agree on a weekly target and whether you’ll inject IM (into muscle) or SC (into the fat just beneath the skin). In practice, a common testosterone cypionate dosage window for TRT is roughly 75–150 mg per week (often split into two shots); the exact number is individualized. Drug references explicitly note that dosing should be individualized to response and adverse effects, not set-and-forget (see the Drugs.com dosage monograph). Monitoring typically includes periodic testosterone levels plus safety checks such as hematocrit, PSA (for men), blood pressure, and lipids to ensure therapy stays effective and safe.
