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Comparison of Intramuscular versus Subcutaneous Testosterone Therapy on Hematocrit Levels
Samantha Freeman, MD, Daniel Pohl, MD, William Du Comb, DO.
Lahey Hospital and Medical Center, Burlington, MA, USA.
Background A known side effect of testosterone replacement therapy (TRT) in men with hypogonadism is elevated hematocrit. Prior studies have suggested that intramuscular and subcutaneous routes may differ in their hematologic effects. This study compares these two routes of TRT while accounting for relevant comorbidities.
Methods A single institution retrospective chart review was conducted of patients receiving subcutaneous or intramuscular TRT since 2019. Patients were excluded if they lacked baseline or post-TRT testosterone or hematocrit values, were under 18 years of age, or had received prior TRT.
Results 100 first-time TRT users were identified, with 50 receiving subcutaneous and 50 receiving intramuscular therapy. There were no significant differences relevant comorbidities between groups (Table 1). Pre-TRT testosterone and pre and post- TRT hematocrit levels did not differ. Post-therapy testosterone levels were significantly higher in the intramuscular cohort (p = 0.0183, Table 2). Subgroup analysis of patients with hematocrits ≥45% demonstrated no significant differences. Linear regression revealed no association between change in testosterone and change in hematocrit after TRT in either cohort (Rē = 0.0007 and Rē = 0.0159, respectively).
Conclusions Post-TRT hematocrit levels did not differ between intramuscular and subcutaneous administration, despite higher post-therapy testosterone levels in the intramuscular group. These findings suggest that the route of TRT may influence serum testosterone without affecting hematologic risk. Importantly, this analysis accounted for key comorbidities.
Table 1. Comparison of relevant comorbidities between intramuscular and subcutaneous TRT patient populations
Table 2. Mean levels of testosterone pre and post testosterone replacement therapy differentiated based on administration
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