Pheochromocytoma with Adrenergic Biochemical Phenotype Shows Decreased Glp-1 Secretion and Impaired Glucose Tolerance.

CONTEXT: Impaired glucose homeostasis is a common finding in pheochromocytoma (PHEO), especially with adrenergic phenotype. The possible contribution of incretin dysfunction to dysglycemia in PHEO patients has not been studied. OBJECTIVE: To compare changes in pancreatic endocrine function and gut hormones' production during a liquid meal test before and one year after adrenalectomy. METHODS: In a prospective study, we included 18 patients with PHEO (13 females) with adrenergic biochemical phenotype. A liquid meal test with predefined isocaloric enteral nutrition was performed to evaluate dynamic changes in pancreatic hormones and incretins. RESULTS: During the meal test, insulin levels were significantly lower before adrenalectomy only in the early phase of insulin secretion, but changes in AUC did not reach statistical significance (AUC = 0.07). Plasma glucagon (AUC < 0.01) and pancreatic polypeptide levels (AUC < 0.01) were suppressed in comparison with the postoperative state. Impaired response to the meal was found preoperatively for GLP-1 (AUC P < 0.05), but not GIP (AUC P = 0.21). No significant changes in insulin resistance indices were found, except for the HOMA-beta index, an indicator of the function of islet beta cells, which negatively correlated with plasma metanephrine (R = -0.66, P < 0.01). CONCLUSIONS: Our study shows suppression of pancreatic alpha and beta cell function and impaired GLP-1 secretion during a dynamic meal test in patients with PHEO, that is improved after its surgical treatment. These data demonstrate a novel and potentially significant interconnection between excessive catecholamine production and the secretion of glucoregulatory hormones.