FASTING, FEASTING, AND FALLING GLUCOSE

A CASE OF NON-INSULINOMA PANCREATOGENOUS HYPOGLYCEMIA SYNDROME FOLLOWING WEIGHT LOSS AND KETOGENIC DIET DISCONTINUATION

Abstract

INTRODUCTION/BACKGROUND
Non-insulinoma pancreatogenous hypoglycemia syndrome (NIPHS) is a rare cause of endogenous hyperinsulinemic hypoglycemia, distinct from insulinoma, often linked to β-cell dysfunction after bariatric surgery in adults.

CASE
This case report describes a previously well 31-year-old male with recurrent hypoglycemia symptoms following intentional weight loss of 44 kg (120 to 76 kg) from practising ketogenic diet for one year. The patient experienced recurrent episodes of giddiness, palpitations and syncope, with lowest capillary blood glucose levels documented as 1.8 mmol/L. These symptoms emerged after resuming a regular carbohydrate diet, after he developed severe constipation with ketogenic diet. The episodes were erratic but reported to be more common after prolonged fasting. Initial evaluation revealed a normal HbA1c (4.7%) with normal hemoglobin (16.5 g/dL), normal morning cortisol and renal and hepatic functions. A supervised 72-hour fast demonstrated symptomatic venous hypoglycemia (2.7 mmol/L) at the 36th hour with inappropriately elevated insulin (5.67 µIU/mL) and C-peptide (496 pmol/L) levels, confirming endogenous hyperinsulinemia. Prolonged oral glucose tolerance testing (OGTT) revealed exaggerated insulin secretion (peak insulin: 43.92 mIU/L at 1 hour; glucose: 8.1 mmol/L), followed by non-suppression of insulin (5.65 mIU/L) and C-peptide (1244 pmol/L) at 4 hours despite low blood glucose of 3.5 mmol/L. Pancreatic CT was normal, supporting a diagnosis of NIPHS. Patient’s symptoms improved following small frequent meals and avoidance of large amounts of simple carbohydrates.

CONCLUSION
This case highlights NIPHS as a consequence of altered β-cell function following prolonged ketogenic diet, likely exacerbated by rapid dietary carbohydrate reintroduction.