Inclusion Criteria:  Informed Consent as documented by signature Biochemically proven endogenous hyperinsulinemic hypoglycemia: neuroglycopenic symptoms in the fasting state with low plasma glucose, inappropriately high serum insulin and C-peptide concentrations (standardized 72h fasting test).).  Exclusion Criteria:  Known hypersensitivity or allergy to Exenatide Pregnant or breastfeeding female patients. A pregnancy test will be performed in all women of child bearing potential. Calculated creatinine clearance below 40 ml/min No signed informed consent Intake of any GLP-1 analogue (such as Byetta® or Bydureon®[= Exenatide]) prediabetes or diabetes (HbA1c > 5.7 %) Previous abdominal surgery in the gastrointestinal tract Any concomitant glucose-lowering drug (i. e. insulin, sulfonyl urea) Any known intolerance to standardized meal (Maizena) Any uncontrolled significant medical, psychiatric or surgical condition (active infection, unstable angina pectoris, cardiac arrhythmia, poorly controlled hypertension, uncontrolled congestive heart disease, etc.) or laboratory findings that might jeopardize the patient's safety or that would limit compliance with the objectives and assessments of the study. Any mental conditions which prevent the patient from understanding the type, extent and possible consequences of the study and/or an uncooperative attitude from the patient