Abnormal sodium and potassium metabolism in orthostatic dysregulation in childhood

Serum sodium (Na) and potassium (K), 12-hr urine Na, K and Na/K ratio and fractional Na excretion rate (FENa) were examined in 142 children with orthostatic dysregulation (O.D.) aged 6 to 15 years. Serum K and FENa were significantly lower in children with O.D. than in normal children, conflicting with the results of low plasma renin activity and aldosterone concentration in children with O.D. which we had previously reported. This suggests that there might be excessive excretion of a mineralocorticoid other than aldosterone or that there might be abnormal regulation of Na and K metabolism by the renin-angiotensin-aldosterone system.