The dopamine agonist bromocriptine has been approved for the treatment of type 2 diabetes in the United States. Bromocriptine inhibits prolactin secretion, and patients with hyperprolactinaemia display impaired insulin sensitivity. We therefore hypothesized that low prolactin levels are associated with lower glycaemia and higher insulin sensitivity in healthy subjects. Prolactin levels were determined from fasting serum in participants without diabetes from the cross-sectional Tübingen family study for type 2 diabetes (m/f=562/1,121, age=40±13years, BMI=30±9kg/m(2)). A 75g oral glucose tolerance test was performed, and the area under the glucose curve (AUC0-120Glucose) and insulin sensitivity index were calculated. A subgroup (n=494) underwent hyperinsulinaemic-euglycaemic clamp tests. Prolactin associated positively with insulin sensitivity (p=0.001, adjusted for gender, age, and BMI). Age strongly interacted (p