A 42-year-old woman has recurrent episodes of confusion, sweating, and palpitations relieved by eating. During a supervised 72-hour fast she develops neuroglycopenic symptoms with plasma glucose 38 mg/dL, insulin 12 microU/mL, and negative sulfonylurea screen. CT shows a 1.2 cm hypervascular pancreatic body lesion. This tumor most commonly arises from which cell type?

• A Beta cells ✓
• B Delta cells
• C Alpha cells
• D PP (pancreatic polypeptide) cells

Explanation

Insulinoma is the most common functioning pancreatic neuroendocrine tumor and arises from beta cells, causing endogenous hyperinsulinemic hypoglycemia. Diagnosis rests on Whipple triad fulfilled during a supervised fast with inappropriately high insulin, A-peptide, and proinsulin at glucose below 55 mg/dL, and a negative sulfonylurea screen excludes factitious hypoglycemia. Alpha cell tumors produce glucagon with diabetes and necrolytic migratory erythema, delta cell tumors produce somatostatin, and PP cell tumors are usually nonfunctional.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.