Evaluation of the Neuro-endocrine Response to Post-prandial Hyperinsulinaemic Hypoglycaemia.

Inclusion criteria for PHH patients (Group 1): * Aged ≥18 years * Roux-en-Y gastric bypass ≥1 year ago * PHH defined as postprandial plasma or sensor glucose\<3.0mmol/l according to the International Hypoglycaemia Study Group (1) and exclusion of other causes of hypoglycaemia Inclusion criteria for non-PHH surgical controls (Group 2 and 3): * Aged ≥18 years * Roux-en-Y gastric bypass (Group 2) or sleeve gastrectomy (Group 3) ≥1 year ago * No evidence of PHH Inclusion criteria for non-PHH non-surgical controls (Group 4): * Aged ≥18 years * Absence of any condition or previous surgery known to affect gastro-intestinal integrity and food absorption Exclusion criteria for all Groups: * Clinically relevant weight changes (≥5%) within the past 3 months * Incapacity to give informant consent * Historical or current diabetes based on HbA1c ≥6.5% without glucose-lowering treatment * Haemoglobin level below 13.5 g/l * Ongoing treatment with glucose-lowering drugs, anorectic drugs, steroids or any medications known to affect gastric motility * Active heart, lung, liver, gastrointestinal, renal or neurological disease * Inability to follow study procedures * Pregnancy or breast-feeding