We performed this study to investigate whether changes in plasma glucose, insulin, and norepinephrine concentrations during an oral glucose tolerance test (OGTT) are associated with changes in plasma leptin levels in normotensive and hypertensive obese women. Plasma insulin, glucose, norepinephrine, and leptin concentrations were evaluated at the baseline and during OGTT in normotensive women (NT-Ob, N = 24, mean age 38.3+/-1.8 years, body mass index [BMI] 37.9+/-1.1 kg/m2) and hypertensive (HT-Ob, N = 25, mean age 37.7+/-1.9 years, BMI 39.4+/-1.3 kg/m2) obese women, and in a group of normal-weight women (controls, N = 20, mean age 38.3+/-1.3 years, BMI 23.1+/-0.4 kg/m2). The OGTT caused a significant increase in plasma leptin concentrations in both NT-Ob and HT-Ob groups, whereas no such change was detectable in control subjects. Area under curve (AUC) for plasma leptin showed a direct correlation with norepinephrine AUC in both NT-Ob (r = 0.73, P = .001) and HT-Ob (r = 0.74, P = .001) group, which was still detectable in multivariate analysis (P = .014 and P = .017, respectively). Our study confirms that glucose loading increases circulating leptin concentrations in obese women, and demonstrates the existance of an association between leptin and norepinephrine changes during OGTT in both normotensive and hypertensive obese women. We hypothesize that this association may reflect the lack of leptin suppression by catecholamines or a direct leptin-induced sympathoactivation. These findings suggest that leptin could be relevant in the regulation of blood pressure in obese women.