Lesson of the month 2: An unusual cause of depression in an older man: Cushing's syndrome resulting from metastatic small cell cancer of the prostate.

This article describes the case of an older patient whose main presenting problem was depression. A constellation of clinical and biochemical features led to a search for medical causes of his low mood, which uncovered ectopic adrenocorticotropic hormone (ACTH) secretion. Post-mortem examination showed that the source of ACTH was small cell neuroendocrine carcinoma of the prostate, and that the patient had died from the sequelae of profound immune suppression. © Royal College of Physicians 2018. All rights reserved.