Purpose We studied the incidence and risk factors for the development of erythrocytosis with implantable testosterone pellets. Materials and Methods A multi-institutional retrospective database analysis was used to evaluate men treated with testosterone pellets between 2009 and 2014. Inclusion criteria consisted of adult, hypogonadal males who had a full complement of pretreatment and posttreatment surveillance studies. Pretreatment and posttreatment values were compared with Wilcoxon signed rank tests. Multiple linear regression was used to identify potential risk factors for significant hematocrit elevation. Results A total of 97 patients were included in the study. The average age of the cohort was 52 years (range 24 to 80). Mean hematocrit before and after pellet implantation was 43.9% and 46.1%, respectively, corresponding to an increase of 2.2% (CI 1.4–2.9, p <0.001). The average increase in testosterone was 145.3 ng/dl from an initial mean of 278.9 ng/dl (CI 105.7–184.9, p <0.001). Multiple linear regression demonstrated that pretreatment hematocrit was inversely related to the expected change in hematocrit. Pretreatment comorbidity status (ie the presence of hypertension, hyperlipidemia, obesity or diabetes) was not associated with a significant increase in posttreatment hematocrit. Conclusions Although the data demonstrate a statistically significant increase in hematocrit, an increment of 2.2% is unlikely to translate into clinical relevance. Thus, for this cohort of patients implantable testosterone pellets appear safe in terms of the risk of polycythemia. Pretreatment hematocrit may serve as a predictor of a significant hematocrit increase after the initiation of therapy.
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