Endocrine Abstracts

We present the case of a 50-year-old male who developed severe hypoglycaemia after Roux-en-Y gastric bypass (RYGB), illustrating the role of selective arterial calcium stimulation test (SACST) in the diagnosis and management of hypoglycemia. Our patient presented with recurrent hypoglycaemia one to two hours after meals, which started 15 years post RYGB performed for morbid obesity with hypertension, impaired glucose tolerance, NAFLD and ischemic heart disease. The hypoglycaemia events were severe and frequent, with glucose levels reaching 39 mg/dl (2.2 mmol/l) associated with altered level of consciousness. During these events, patient had high insulin (1086 pmol/l), proinsulin (26.2 pmol/l), and C-peptide (6.08 nmol/l) levels, normal levels of beta-hydroxybutyric acid, with negative sulfonylurea screen, negative insulin antibodies and normal IGF2 levels, all suggestive of endogenous hyperinsulinemia. The patient failed to have hypoglycaemia during a mixed meal test and a 72- hour fast. He had normal thyroid, kidney and adrenal function tests. Imaging and functional studies of the pancreas and abdomen were negative; these included abdominal computed tomography, abdominal magnetic resonance imaging and Gallium Dotatate PET CT. In addition, endoscopic ultrasound (EUS) was performed and did not show any pancreatic masses. Acarbose was initiated with dietary modification which included a low carbohydrate and high protein diet, however, hypoglycaemia episodes persisted. He was then started on daily octreotide injections and nifedipine. The hypoglycaemia episodes became less severe and less frequent subsequently. To further investigate the source of endogenous hyperinsulinemia in our patient, a selective arterial calcium stimulation test (SACST) was performed in order to differentiate between insulinoma (uni or multifocal) and non-insulinoma pancreatogenous hyperinsulinemia. This showed two to threefold increase in insulin levels post arterial calcium stimulation in all pancreatic regions and no tumor blush was observed. Therefore, the test did not localize a focal region of the pancreas that is responsible for excess insulin secretion and that would be amenable to surgery. Lastly, he was not a candidate for gastrojejunostomy stoma reduction/plication as there was evidence of Roux-en-Y anatomy with a micro pouch on upper endoscopy. Reversal of the bypass was also discussed but not pursued given patient’s morbid obesity and overall poor health condition. The decision was to continue with medical and dietary therapies for non-insulinoma pancreategenous hyperinsulinemia. Our case illustrates the importance of SACST in the evaluation of endogenous hyperinsulinemic hypoglycaemia with negative localization studies. In this case, it spared the patient from undergoing an additional highly morbid surgery (pancreatectomy).