c-peptide and Pheochromocytoma

Pheochromocytoma usually is associated with a combination of various manifestations caused by overproduction of catecholamines. We encountered a case of an occult, catecholamine-secreting pheochromocytoma. A 70-year-old man was admitted to the hospital because of anorexia. He had been treated for diabetes mellitus for 4 years; during this period he did not have any other symptoms related to pheochromocytoma. At admission, serum epinephrine, norepinephrine, and glucose levels and urinary excretion of total metanephrine were elevated. A tumor was detected in the left adrenal region and diagnosed as pheochromocytoma. After tumor resection, the increased levels of catecholamines and glucose and the decreased urinary C-peptide were normalized. This suggests that the pheochromocytoma caused hyperglycemia without other manifestations for a long time.

Topics: Aged; Blood Glucose; C-Peptide; Catecholamines; Diabetes Mellitus; Diagnostic Errors; Humans; Hyperglycemia; Insulin; Male; Pheochromocytoma; Tomography, X-Ray Computed

The finding of hypoglycemia after the surgical removal of a pheochromocytoma in two patients in a previous study led to monitoring of the serum glucose and plasma C-peptide levels in two other patients with a pheochromocytoma and one with unilateral adrenocortical hyperplasia. In the two patients with a pheochromocytoma endogenous insulin secretion, as measured by a C-peptide assay, was suppressed before removal of the tumours and resumed immediately after removal. The serum glucose levels decreased in these patients, but sufficient intravenous administration of glucose prevented postoperative hypoglycemia. In the patient with adrenocortical hyperplasia the plasma C-peptide level was not decreased before tumour removal, nor did it increase abruptly following removal. It therefore seems likely that the rapid fall in the serum glucose level following removal of a pheochromocytoma is caused by prompt resumption of beta-cell activity, with rebound hyperinsulinism.

Topics: Adrenal Cortex Diseases; Adrenal Gland Neoplasms; Blood Glucose; C-Peptide; Female; Humans; Hyperinsulinism; Hyperplasia; Male; Middle Aged; Pheochromocytoma; Postoperative Complications