Endocrine Abstracts

Background: Bariatric surgery has contributed to a large spectrum of presentations of hypoglycaemia. Dumping syndrome caused by food reaching the duodenum rapidly is associated with abdominal pain, bloating and diarrhoea as well as vasogenic symptoms of tachycardia and flushing. Hypoglycaemia may occur as a late sign of dumping 1–3 hours after a meal. In contrast, post-gastric bypass reactive hypoglycaemia is thought to result from discordance between blood glucose circulation and insulin secretion. We report a case of reactive hypoglycaemic via oral glucose tolerance test (OGTT) in the absence of classical features of dumping syndrome immediately post-carbohydrate load.

Case report: A 59-year old lady was referred with light-headedness on and off for 3 years coinciding with tingling in her back, arms and lower limbs. These intermittent episodes last for up to 10 minutes, without any seizures. There is absence of clinical features of dumping syndrome up to 30 minutes after meals. She had a roux-en-Y gastric bypass surgery 7 years ago with co-morbidities including ischaemia heart disease, hypertension, hypercholesterolaemia, and arthritis. OGTT was performed by administering a 75 g oral glucose load, during which she had a nadir venous glucose of 2.2 mmol/l confirming the diagnosis of reactive hypoglycaemia. She had no features of dumping syndrome. Incidentally she had low zinc levels, 10.1 μmol/l (normal range 11.5–18.5 μmol/l) but normal vitamin B12, folate, ferritin, iron, vitamin D and lipid profile. Her gut hormones including glucagon, vasoactive intestinal peptide, chromogranin A, somatostatin and gastrin were all within normal limits. With dietary modification and dietician advice she managed to control her symptoms.

Discussion: Since Mayo report by Service et al. in 2005, it is hypothesised that post-prandial hypoglycaemia may be due to endogenous hyperinsulinaemia from abnormal islets, as a result of nesidioblastosis.

Conclusion: OGTT for reactive hypoglycaemia should be performed in a monitored environment. However, we should be cautious on patient selection for OGTT due to increasing reported incidence of adverse effects (64.8%) and hypoglycaemia (14.8%) during test in post-bariatric surgery patients.