Gastric carcinoid with ectopic production of ACTH and beta-MSH.

A 51-year-old woman with typical Cushing's syndrome of about 9 years duration was shown to have a gastric carcinoid tumor. Plasma levels of ACTH and cortisol were elevated and lacked the normal diurnal rhythm. Urinary excretion of steroids was unaffected by the administration of either metyrapone or dexamethasone. Fluctuation in urinary steroid excretion, as well as transient hypokalemic alkalosis and glycosuria suggested periodic hormonogenesis. The extirpated gastric carcinoid was shown to contain immunoreactive ACTH and beta-MSH. However, the biologic ACTH activity was undetectable by in vivo steroidogenic assay. By gel filtration, it was demonstrated that both tumor and plasma ACTH was predominately "big" ACTH. Although postoperatively she developed hypoadrenocorticism severe enough to require ACTH treatment, her pituitary-adrenal function was gradually restored. This is the first documented case of ectopic ACTH syndrome caused by gastric carcinoid in which successful cure was achieved by surgery.