Endocrine pancreatic function in pheochromocytoma

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 1 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 area under the curve (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 glucagon-like peptide-1 (GLP-1; AUC P < 0.05), but not glucose-dependent insulinotropic polypepide (GIP; AUC P = 0.21). No significant changes in insulin resistance indices were found, except for the homeostatic model assessment-beta index, an indicator of the function of islet β cells, which negatively correlated with plasma metanephrine (R = -0.66, P < 0.01).

CONCLUSIONS

Our study shows suppression of pancreatic α and β cell function and impaired GLP-1 secretion during a dynamic meal test in patients with PHEO, which 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.

Pheochromocytoma. Update on diagnosis, localization, and management

Pheochromocytoma, although rare, is associated with a high degree of morbidity and mortality if not recognized. A high degree of suspicion in patients with new-onset hypertension; hypertension with sudden worsening or development of diabetes mellitus; or a family history of MEN, neuroectodermal tumors, or simple pheochromocytoma should prompt biochemical confirmation with either 24-hour urine catecholamines (norepinephrine and epinephrine) or total MET (NMET plus MET). Following confirmation of the diagnosis, radiologic studies with CT and (if needed) MIBG are employed to localize the tumor. Surgical removal is the only definitive therapy. Medical management with alpha-blocking agents, to control symptoms and prevent a hypertensive crisis, is generally advocated for 2 weeks preoperatively and intraoperatively. Occasionally, beta-blockers, employed only after adequate alpha-blockade, are necessary to control tachycardia and tachyarrhythmias. High-dose MIBG and combination chemotherapy have been used adjunctively to treat malignant pheochromocytoma, although neither modality provides lasting satisfactory results. Normal urine assays performed 2 weeks postoperatively ensure the complete removal of all tumor. Additionally, lifelong follow-up (yearly initially) is necessary to detect any signs of benign recurrence or malignancy because these have been reported to occur as long as 41 years after the initial surgical resection. Biochemical evidence of excess catecholamine production usually precedes the clinical manifestations of catecholamine excess when these tumors recur.

Necrosis of a phaeochromocytoma associated with spontaneous remission of diabetes and hypertension

The diagnosis of phaeochromocytoma is sometimes difficult since its clinical presentation is quite variable. We report a 52-year-old woman who presented with acute diabetes mellitus and severe hypertension, which spontaneously disappeared. MIBG-scintigraphy and urine and plasma catecholamines were normal. At surgery, a largely necrotic phaeochromocytoma was found. Pathological examination demonstrated extensive avascular necrosis, which had occurred spontaneously without any major symptoms.