Does a GLP-1 Receptor Agonist Change Glucose Tolerance in Antipsychotic-treated Patients?

Inclusion Criteria: * Informed oral and written consent * Diagnosed with schizophrenia, schizotypal disorder or paranoid psychosis according to the criteria of ICD10 (International Classification of Diseases, World Health Organization) or the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, the American Psychiatric Association) * and on stable antipsychotic treatment with either clozapine or olanzapine for at least 6 months (without dose change for at least 30 days) * Stable co-medications for at least 30 days. * Age ≥18 years and ≤65 years * Stable weight (defined as less than 5% change in weight over the last 3 month before inclusion) * BMI ≥27 kg/m2 * Dysglycaemia (IFG, i.e. fasting plasma glucose level from 6.1 mmol/L to 6.9 mmol/L or IGT, i.e. two-hour glucose levels \> 7.8 mmol/L on the 75-g oral glucose tolerance test with a fasting plasma glucose of less than 7.0 mmol/L and HbA1c \< 48 mmol/mol or HbA1c: 43 mmol/mol ≤ HbA1c ≤ 47 mmol/mol) Exclusion Criteria: * Compulsory treatment * Females of child bearing potential who are pregnant, breast-feeding or have intention of becoming pregnant or are not using adequate contraceptive measures * Subjects treated with corticosteroids or other hormone therapy (except estrogens) * Any active substance abuse or dependence for the past 6 months (except for nicotine) * Impaired hepatic function (liver transaminases \>2 times upper normal limit) * Impaired renal function (se-creatinine \>150 μM and/or macroalbuminuria) * Impaired pancreatic function (acute or chronic pancreatitis and/or amylase \>2 times upper normal limit) * Cardiac problems defined as decompensated heart failure (NYHA class III or IV), unstable angina pectoris and/or myocardial infarction within the last 12 months * Uncontrolled hypertension (systolic blood pressure \>180 mmHg, diastolic blood pressure \>100 mmHg) * Any condition that the investigator feels would interfere with trial participation * Receiving any investigational drug within the last 3 months * Use of weight-lowering pharmacotherapy within the preceding 3 month * Type 1 or 2 diabetes with HbA1c \> 6.5% Also a group of healthy controls (n=10) will have the baseline examinations done. The healthy controls will be matched to our participants in regards to gender, BMI and age. The same inclusion and exclusion criteria will apply for these controls, except these participants are not allowed to have known psychiatric illness, receive anti-psychotic medications, or have a family history of type 2 diabetes (2 generations).