In this study the investigators will investigate the effect of dopamine (bromocriptine) on Brown Adipose Tissue in lean, young, healthy males.

The investigators will also examine energy expenditure, body temperature and insulin sensitivity as measurements of Brown Adipose Tissue activity.

In this study the investigators will investigate whether bromocriptine influences the metabolic activity of BAT, as assessed with a 18F-fluorodeoxyglucose (18F-FDG) Positron Emission Tomography (PET)-CT scan

This is an observational, prospective design with invasive measurements. The investigators will include 16 healthy lean male volunteers (aged 18-30 years, BMI 19-25 kg/m2) The volunteers will be recruited by advertisement in local paper and internet (via social media), covering the direct surroundings of our clinic (Amsterdam) and by advertisement at the medical faculty of the Academic Medical Center (AMC).

The included subjects will visit the AMC hospital on 3 occasions. During visit 1 the investigators will obtain the Informed consent after oral and written information about the study. The investigators will obtain a medical history, vital signs and laboratory measurements.

During visit 2 the investigators will measure body weight and the investigators will perform an energy expenditure measurement after 40 minutes of bed rest. The investigators will regularly measure temperature by a tympanic thermometer. The subjects will receive intravenous administration of the radioactive pharmacon 18F-FDG, 60 minutes after the administration of the 18F-FDG, and 18F-FDG PET-CT scan will be performed. After the 18F-FDG PET CT scans, the investigators will measure insulin sensitivity by performing an oral glucose tolerance test.

After this visit, subjects will start using bromocriptine (1,25mg/day during the first week and 2,50mg/day during the second week) in the evening.

Visit 3(2 weeks after visit 2) will be exactly the same as visit 2. In the three days before visit 2 and 3, subjects will record their eating behaviour.

Inclusion Criteria:

• Male
• Caucasian origin
• Subjects should be able and willing to give informed consent
• 18-30 years old
• BMI range of 19-25 kg/m2

Exclusion Criteria:

• Renal failure (creatinine>135mmol/l)
• Liver failure (AST/ (Alanine Aminotransferase) ALT > 3 times higher than the normal upper value)
• Daily use of prescription medication
• Known hypersensitivity to bromocriptine, domperidone maleate or other ergot alkaloids.
• Uncontrolled hypertension
• Known history of coronary artery disease, or other severe cardiovascular conditions (such as a prolonged Qtc-time), or symptoms / history of severe psychiatric disorders.
• Known cardiac valvulopathy
• Prolactin-releasing pituitary tumor (prolactinoma).
• Cases where stimulation of the gastric motility could be harmful: gastro-intestinal haemorrhage, mechanical obstruction or perforation.
• Subjects with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
• Prior participation in a research protocol involving radiation exposure in the last 2 years