Trough serum testosterone predicts the development of polycythemia in hypogonadal men treated for up to 21 years with subcutaneous testosterone pellets

ObjectivesTestosterone formulations that have more steady-state pharmacokinetics, such as subcutaneously implanted testosterone pellets, may cause less erythrocytosis than i.m. injections of shorter acting androgen esters. We, therefore, sought to define the prevalence, predictors, and proximate basis (role of erythropoietin) for polycythemia (hematocrit >0.50) in hypogonadal men receiving testosterone implants long term.DesignA cross-sectional study was conducted in an academic andrology center with a longitudinal subgroup analysis.PatientsA total of 158 hypogonadal men aged 14–84 years (mean age 46.7 years) treated on average for 8 years (range 0–21 years).MeasurementsTrough blood testosterone and hematocrit. Serial serum erythropoietin concentrations were measured in 16 volunteers.ResultsPositive univariate associations between polycythemia (hematocrit >0.50) and log(testosterone) (odds ratio (OR) 24.7, 95% confidence interval (CI): 4.3, 141.2, P