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Presentation of a case of Sipple's syndrome with bilateral malignant pheochromocytoma, bilateral thyroid medullary carcinoma and two parathyroid adenomas. The principal characters of the syndrome, the diagnostic tests, the necessity of a prospective survey of family relatives are discussed.

A patient is described in whom the diagnosis of pheochromocytoma was suspected on clinical grounds. He had normal urinary and plasma norepinephrine levels, with normal suppression of plasma norepinephrine by clonidine. However, plasma and urinary epinephrine levels were above normal, and plasma epinephrine was not suppressed but increased by clonidine. Selective venous sampling showed marked unilateral adrenal epinephrine excess. A large epinephrine secreting pheochromocytoma was surgically removed. This case suggests that, in pheochromocytomas releasing predominantly epinephrine, normal norepinephrine release from axon terminals of sympathetic postganglionic neurons is maintained and is suppressed by clonidine administration. It further reaffirms the value of plasma epinephrine estimations in the diagnosis of pheochromocytoma and indicates that normal suppression of plasma norepinephrine by clonidine does not preclude the presence of a predominantly epinephrine secreting tumor.

A case of MEN type IIa is described showing among other symptoms, three attacks of transient neurological symptoms. These were attributed to a localized, transient cerebral ischemia. The latter probably developed as a consequence of the concomitant occurrence of different phenomena: the existence of hypercalcemia and on the other hand the secretion of vasoactive substances by one of the three tumours forming the MEN type IIa syndrome. The pheochromocytoma played an essential role because the symptoms did not recur after the bilateral adrenalectomy.