Endocrine Abstracts

Introduction/case report: Diabetes mellitus is an important clinical manifestation of catecholamine excess in patients with pheochromocytoma, and glucose control is usually better after tumour removal. Both impaired insulin secretion and increased insulin resistance have been implicated as underlying causes. We describe the case of a 38-year-old male patient diagnosed with left adrenal pheochromocytoma and personal history of diabetes mellitus diagnosed at age 36, under treatment with metformin, saxagliptin and gliclazide, with a preoperative HbA1c of 7.2%. BMI of the patient was 23 kg/m². After successful pheochromocytoma removal, the anti-diabetic medication was immediately stopped with remission of diabetes mellitus (HbA1c 3-months-postoperative 5.7%).

Methods: We performed oral glucose (75 g) tolerance tests and measured venous plasma glucose and serum insulin levels at the time of diagnosis and three months after successful surgery, to derive the insulinogenic index (IGI) as proposed by Wareham, and whole body insulin sensitivity index (ISI) as proposed by Matsuda and DeFronzo.

Results: Plasma glucose and serum insulin levels are shown in the table 1.

Improved glucose levels were associated with increased insulin levels and an increase in IGI, from a preoperative value of 5.7–33.6 pM/mM, while the ISI remained unchanged.

Conclusion/discussion: Remission of diabetes mellitus in our patient was associated with marked improvement of insulin secretion and oral glucose tolerance after removal of pheochromocytoma. Adrenergic alpha2A receptors on pancreatic beta cells play an important role in mediating inhibitory effects of catecholamines on insulin release, according to recent genetic association and pharmacological intervention studies. In our case, impaired insulin secretion could be corrected by surgery.