[Renin-angiotensin-aldosterone system in obese children]

Plasma renin (PRA) and aldosterone activities were measured in 29 obese children and in 48 controls of the same age. Blood samples were taken at 8 AM after a night's sleep and after 3 days of a diet with normal sodium intake. The PRA in the obese children was lowered: m = 1.00 ng/ml/h (controls = 1.86 ng/ml/h; p = 0.01). The drop in plasma aldosterone activity was not significant: m = 134.1 pg/ml (controls: m = 167.5 pg/ml). Plasma aldosterone activity was positively correlated with PRA in controls (p less than 0.01): this correlation was not found in obese children. In obese children no dissociation could be found, in the resting state, between plasma aldosterone activity and PRA, contrary to obese adults under stimulation. In fact, 1) the aldosterone/PRA ratio did not differ significantly between obese children and controls, 2) the average value of plasma aldosterone activity that one could predict in the obese children from their average PRA level and the linear regression calculated from the controls exactly corresponded to the measured value. The elevated blood pressure found in the obese children could explain the drop in the PRA which would thus remain adapted to the blood pressure level.