Seize the diagnosis: insulinoma masquerading as post-bariatric hypoglycaemia — ASN Events
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Seize the diagnosis: insulinoma masquerading as post-bariatric hypoglycaemia (#414)

Anya Gnanasekaram 1 , Purnima Cheruvu 1 , Caitlin Corkhill 1 , Timothy Greenaway 1 2
  1. Department of Endocrinology and Diabetes , The Canberra Hospital , Canberra, ACT, Australia
  2. School of Medicine, Faculty of Health, University of Tasmania, Hobart, Tasmania, Australia

Hyperinsulinemic hypoglycaemia is a recognised complication following bariatric surgery and is most commonly attributed to post bariatric hypoglycaemia (PBH), or less commonly, nesidioblastosis (1). The diagnosis of an insulinoma following sleeve gastrectomy is rare and predominantly presents with post prandial hypoglycaemia (2).

We present a 47-year-old woman with a history of laparoscopic sleeve gastrectomy and abdominoplasty for class III obesity who presented with a one-year history of recurrent post prandial hypoglycaemic episodes of increasing frequency despite 8-week trial of semaglutide, she was initially diagnosed with PBH. She was admitted to hospital following a generalised tonic-clonic seizure secondary to severe symptomatic hypoglycaemia symptoms fulfilling Whipple’s triad with blood glucose levels (BGL) of 2.8-3.0 mmol/L.

Biochemical investigations confirmed endogenous hyperinsulinism (BGL 1.9 nmol/L with paired C-peptide 1.6 nmol/L (RR 0.4-1.5 nmol/L) and insulin 15 mU/L (RR <3 mU/L). Despite escalation of conventional therapies with titration of diazoxide to 100mg three times daily, concurrent continuous glucose infusion, trial of dexamethasone therapy and octreotide infusion, the patient had recurrent neuroglycopenia requiring Intensive Care Support (Figure 1).

Contrast - enhanced CT failed to identify a pancreatic lesion; however, Gallium-68 DOTATATE PET Scan demonstrated focal uptake within the uncinate process, with MRI confirming a 15 × 18 mm pancreatic lesion (Figure 2). Urgent pancreatoduodenectomy was performed and histopathology demonstrated a 21 mm WHO Grade 1 well-differentiated pancreatic neuroendocrine tumour with insulinoma phenotype (Ki-67 <1%).

This case highlights the potential for insulinoma to mimic PBH and demonstrates that post prandial symptoms do not exclude an insulinoma (3,4). Progression to fasting and nocturnal hypoglycaemia when accompanied by failure of conventional therapy should prompt reconsideration of diagnosis and alternate causes of Hyperinsulinemic hypoglycaemia. Functional imaging may identify lesions occult on cross sectional imaging, facilitating earlier definitive surgical management preventing recurrent life threatening neuroglycopenia.

  1. Service GJ, Service FJ, Thompson GB, Andrews JC, Collazo-Clavell ML, Lloyd RV. Hyperinsulinemic Hypoglycemia with Nesidioblastosis after Gastric-Bypass Surgery. The New England journal of medicine. 2005;353(3):249-54.
  2. Malik S, Mitchell JE, Steffen K, Engel S, Wiisanen R, Garcia L, et al. Recognition and management of hyperinsulinemic hypoglycemia after bariatric surgery. Obesity research & clinical practice. 2016;10(1):1-14.
  3. Qian SY, Hare MJL, Pham A, Topliss DJ. Insulinoma presenting with post-prandial hypoglycaemia following fundoplication. Endocrinology, diabetes & metabolism case reports. 2018;2018(1):1-6.
  4. Placzkowski KA, Vella A, Thompson GB, Grant CS, Reading CC, Charboneau JW, et al. Secular Trends in the Presentation and Management of Functioning Insulinoma at the Mayo Clinic, 1987–2007. The journal of clinical endocrinology and metabolism. 2009;94(4):1069-73.