In order to evaluate the difference in beta cell mass in patients with and without hyperinsulinemic hypoglycemia after Roux en Y gastric bypass (RYGB) investigators aim to compare quantitative PET imaging of the pancreas between these patient groups.

These highly relevant data will provide investigators with more information on the possible role of beta cell mass in the mechanisms of hyperinsulinemic hypoglycemia bariatric surgery.

Inclusion Criteria:

• Signed informed consent

Patients:

- Persisting hyperinsulinemic hypoglycemia after a low-carbohydrate diet and/or insulin suppressive medication for one year.

Controls:

• RYGB at least 2 years ago
• Normal glucose levels before and after RYGB (fasting glucose between 4 and 6 mmol/l or HbA1c between 20 and 42 mmol/mol)
• Score ≤ 7 on Sigstad's scoring system (Table 1)
• Hypoglycemia excluded by 14-day continuous glucose monitoring
• Individual matched to HH group on age (± 5 years), sex and BMI at time of inclusion (± 2 kg/m2)

Exclusion Criteria:

• Anti-diabetic medication in the past 6 months
• Treatment with synthetic Exendin (Exenatide, Byetta®) or Dipeptidyl-Peptidase IV inhibitors in the past six months.
• Known liver failure or serum liver values over 2 times normal value at the time of standard laboratory assessment. Normal values of total bilirubin, γ-GT, ASAT and albumin are <21 μmol, <40 U/l, <30 U/l and 35-50 g/l respectively
• Pregnancy or the wish to become pregnant within 6 months
• Breast feeding
• Kidney failure, i.e. calculated creatinine clearance below 40 ml/min
• Age < 18 years
• No signed informed consent