Reversible Gynecomastia Induced by Darbepoetin in a Patient With Chronic Kidney Disease.

Gynecomastia is a benign proliferation of the glandular tissue of the male breast. It is a common physiological condition during infancy and puberty and typically resolves spontaneously in most cases. However, adult-onset gynecomastia requires proper evaluation to identify the underlying cause. Several medications are associated with gynecomastia in adults, with some having a clear pathophysiologic mechanism while others do not. We report a 78-year-old male with chronic kidney disease (CKD) who developed painful gynecomastia following the administration of darbepoetin. The gynecomastia resolved upon cessation of darbepoetin but recurred upon its reintroduction. Extensive evaluation did not identify any other underlying cause. To our knowledge, this is the first case describing an association between darbepoetin and gynecomastia. In addition to presenting the case, we briefly discuss the hormonal changes in CKD patients and the potential effects of synthetic erythropoiesis-stimulating agents (ESAs) on hormone regulation.