Corticotropin-releasing hormone-producing medullary thyroid carcinoma causing Cushing's syndrome: Clinical and pathological findings

A 62-yr-old woman presented with progressive fatigue and weakness and was found to have hypercalcemia due to a parathyroid adenoma. Following resection of the adenoma, she developed intractable diarrhea with progressive weakness. Further evaluation showed very high serum calcitonin levels and high cortisol and adrenocorticotropic hormone (ACTH) levels along with elevated urinary 5-hydroxindole acetic acid (5-HIAA) levels. Liver biopsy showed metastatic medullary thyroid carcinoma which did not stain positively for ACTH but stained positively for corticotropin-releasing hormone (CRH) and serotonin. Further examination of the parathyroid tissue showed medullary thyroid carcinoma cells invading the adenoma. This is the first report of a patient with hyperparathyroidism and metastatic medullary carcinoma of the thyroid producing serotonin and CRH resulting in Cushing's syndrome.