Prolonged suppression of a corticotropin-producing bronchial carcinoid by oral bromocriptine

The addition of orally administered bromocriptine mesylate to cyproheptadine hydrochloride therapy completely normalized urinary-free cortisol levels for three months in a 21-year-old woman with Cushing's syndrome in whom results from standard dexamethasone suppression and metyrapone stimulation tests as well as baseline corticotropin levels were originally compatible with a diagnosis of an occult pituitary adenoma. When transsphenoidal exploration of the sella turcica was unsuccessful and hypercortisolism persisted, the source of corticotropin was discovered using petrosal sinus and venal caval catheterization. A 1 X 1.5-cm carcinoid tumor of the lung was identified and removed, thereby correcting the hypercortisolism. The tumor was demonstrated by immunoperoxidase staining to contain corticotropin. Orally administered bromocriptine, with or without cyproheptadine therapy, may be useful in the palliative treatment of some patients with carcinoid or other ectopic corticotropin-producing tumors. We postulate that bromocriptine therapy acted directly on carcinoid tumor cells to directly inhibit corticotropin production by a dopaminergic mechanism.