Insulin secretion and insulin sensitivity before and after surgical treatment of pheochromocytoma or paraganglioma.

Context: Pheochromocytoma and paraganglioma are catecholamine-producing tumors that often impair glucose tolerance. The effects of these tumors on insulin sensitivity and insulin secretion in patients have remained unclear, however. Objective: To characterize the influence of pheochromocytoma or paraganglioma on glucose tolerance, we comprehensively analyzed various parameters related to insulin secretion or insulin sensitivity in patients with these tumors. Design: Hyperglycemic and hyperinsulinemic-euglycemic clamps, as well as an oral glucose tolerance test (OGTT), were performed in patients before and after tumor excision. Setting: Patients underwent metabolic analyses on admission to Kobe University Hospital. Patients: Eleven patients with pheochromocytoma and two with paraganglioma were examined. Intervention: None. Main Outcome Measures: We evaluated various parameters related to insulin secretion or insulin sensitivity as determined by an OGTT and by hyperglycemic and hyperinsulinemic-euglycemic clamp analyses. Results: Surgical treatment of the tumor reduced urinary catecholamine excretion and improved glucose tolerance. The insulinogenic index, but not total insulin secretion, measured during the OGTT as well as the first phase, but not the second phase, of insulin secretion during the hyperglycemic clamp were improved after surgery. The insulin sensitivity index determined during the hyperinsulinemic-euglycemic clamp remained unchanged after surgery. Conclusion: These results suggest pheochromocytoma and paraganglioma impair glucose tolerance primarily through impairment of insulin secretion-in particular, that of the early phase of the insulin secretory response. A prospective study with more patients is warranted to further confirm these results.