Dr. Marco Marcelli is a physician-scientist interested in clinical and molecular endocrinology. As a clinician, he has been an attending physician in endocrinology consult services and clinics for many years. His specific clinical interests are in the testicular and adrenal glands' diseases. However, he has also cared for innumerous patients with diabetes and thyroid disorders. Dr. Marcelli has been involved in clinical investigations related to diabetes, testicular function, and the effect of traumatic brain injury and opioids on the pituitary gland's physiology. As a basic scientist, he has been interested in the molecular basis of testosterone action. His group has been involved in many contributions to this field, including cloning the androgen receptor and performing studies to identify the mechanisms responsible for prostate cancer's transition to the castration-resistant phenotype. For the last five years, Dr. Marcelli has been the acting chief of the Baylor College of Medicine section of endocrinology and had administrative duties related to this assignment.