Testosterone therapy-induced erythrocytosis: can phlebotomy be justified?

Abstract

Erythrocytosis, or elevated hematocrit, is a common side effect of testosterone therapy (TTh) in male hypogonadism. Testosterone stimulates erythropoiesis through an initial rise in erythropoietin (EPO), establishment of a new EPO/hemoglobin 'set point', and a parallel decrease in the master iron regulator protein hepcidin, as well as several other potential mechanisms. Evidence shows an increased thrombotic risk associated with TTh-induced erythrocytosis. Several guidelines for the treatment of male hypogonadism by endocrine organizations recommend against starting TTh in patients presenting with elevated hematocrit at baseline or to stop TTh when its levels cannot be controlled by dose-adjustments. Importantly, therapeutic phlebotomy or venesection is mentioned as a means of reducing hematocrit in these patients. However, evidence supporting the efficacy or safety of therapeutic phlebotomy in lowering hematocrit in TTh-induced erythrocytosis is lacking. In light of this dearth of evidence, the recommendation to lower hematocrit using therapeutic phlebotomy is notable, as phlebotomy lowers tissue oxygen partial pressure (pO2) and, eventually, depletes iron stores, thereby triggering various biological pathways which might also increase thrombotic risk. The potential pros and cons should therefore be carefully weighed against each other and shared decision making is recommended for initiating therapeutic phlebotomy as a treatment in patients on TTh who present with increased hematocrit.