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Some studies have shown a clustering of obesity, insulin and hypertension. The present study was performed to further characterize these associations.In a population of 51-year-old men (n = 284), measurements of systolic and diastolic blood pressure were analyzed in relation to general obesity (body mass index) and central obesity (waist: hip circumference ratio and abdominal sagittal diameter), and to the fasting insulin and insulin: glucose ratio as an approximation of insulin sensitivity. The regulation of diurnal cortisol secretion was examined in repeated salivary samples.Linear regression analysis showed that all three parameters of obesity were significantly and strongly related to both systolic and diastolic blood pressure, more powerfully than insulin, glucose and insulin sensitivity (insulin: glucose ratio). Stepwise multiple regression showed that only central obesity, measured as the abdominal sagittal diameter, remained significantly (P < 0.001), and independently of insulin and insulin sensitivity, associated with both systolic and diastolic blood pressure (β = 7.5 and 4.2, respectively). A diurnal cortisol curve with normal rhythm was associated with lower than average blood pressures (P < 0.001) but not with insulin levels or the heart rate. In contrast, a flattened diurnal cortisol curve, indicating perturbations in the activity of the hypothalamic-pituitary-adrenal axis, was directly related to blood pressures, heart rate and insulin (P < 0.001), and has previously been found to be strongly associated with abdominal obesity.These findings suggest that general and central obesity is independently related to blood pressure, and that insulin may account for only part of this association. The activity of the hypothalamic-pituitary-adrenal axis is apparently important for blood pressure regulation, suggesting that mechanisms of the central nervous system have an impact.