Abnormal regulation of antidiuretic hormone in idiopathic edema

Idiopathic edema is characterized by impaired water excretion, particularly in the upright posture. Indirect evidence has shown that antidiuretic hormone is involved in this disease. For this reason, we measured urinary arginine vasopressin by radioimmunoassay before and during water loading (15 ml/kg) in 10 normal women and in 10 subjects with idiopathic edema in both the supine and upright postures. Daily sodium intake was 100 meq. Renin and aldosterone were concomitantly investigated, and abnormally high values were observed both in the recumbent and upright postures. Basal values for urinary arginine vasopressin were identical in control subjects and in patients with idiopathic edema. The water load significantly reduced urinary arginine vasopressin in normal women in both positions, but in those with idiopathic edema only in the supine position. In those with idiopathic edema, assumption of the upright posture was accompanied by a transient decrease in glomerular filtration, a major decrease in osmolar clearance and no decrease in urinary arginine vasopressin after water loading. Significant correlations were established between urinary arginine vasopressin and osmolar or volemic parameters in normal women, but these correlations were not found in those with idiopathic edema in either position. Arginine vasopressin regulation was abnormal in idiopathic edema, and this hormone was believed to play a part in the pathogenesis of this disease.