Hyperinsulinemic hypoglycemia (HH) is a rare complication that occurs 1 to 5 years after gastric bypass surgery. The underlying mechanism of this complication is not yet completely understood. Changes in hormone levels, such as GLP1 after RYGB, nesidioblastosis or an increase in the number of beta cells may be one of the underlying causes. However, several study results are conflicting and it is hypothesized that the patient population with HH after RYGB is heterogeneous and several underlying causes may be present. In order to differentiate between hyperfunction with normal beta cell mass and a general or localized increase in beta cell mass we aim to compare quantitative 68Ga-exendin-4 PET imaging of the pancreas between patients with and without HH after RYGB. Thereby, investigators aim to increase the insight in the underlying mechanism of HH after RYGB. If different underlying causes can be diagnosed, treatment for HH can be optimized for patients.