Case 63 - Cushing Syndrome Associated With Ectopic Corticotropin and Corticotropin-Releasing Hormone–Secreting Pheochromocytoma

Abstract

Most patients with corticotropin (ACTH)-dependent Cushing syndrome (CS) will have an ACTH-secreting pituitary microadenoma. Approximately 15% of patients with ACTH-dependent CS have an ectopic source of ACTH secretion. The most common neoplasms associated with ectopic ACTH secretion are bronchial carcinoid (≈25%), pancreatic neuroendocrine tumor (≈16%), occult and unlocalized tumor (≈16%), small cell lung cancer (≈11%), medullary thyroid carcinoma (≈9%), other neuroendocrine tumors (≈7%), thymic carcinoid (≈5%), and pheochromocytoma (≈3%). The main clues that a patient may have ectopic ACTH-dependent CS include severe CS as evidenced by spontaneous hypokalemia and 24-hour urinary free cortisol (UFC) >1000 mcg, rapid onset of CS (sometimes so rapid that there is not time to develop the typical physical stigmata of CS), previous diagnosis of a neuroendocrine tumor, and male sex. Herein we present a case of ectopic secretion of ACTH and corticotropin-releasing hormone (CRH) from a pheochromocytoma causing severe CS.