Testosterone therapy and secondary erythrocytosis

Secondary erythrocytosis is one of the most common adverse events associated with testosterone therapy (TT). Upon encountering this, clinicians will often either adjust TT dosing, stop therapy, order a phlebotomy, or recommend a combination of these. Despite this, the evidence for secondary polycythemia causing harm during TT is scarce, and the hematocrit-based cutoffs present in multiple guidelines appear to be arbritrarily chosen. In this review, we present the pathophysiology behind TT and secondary erythrocytosis, the evidence connecting TT, secondary erythrocytosis and major adverse cardiovascular events (MACE), and the data supporting varying interventions upon diagnosis of secondary erythrocytosis.