Inappropriate secretion of antiduretic hormone, hypertension, and hypoplastic corpus callosum.

The threshold of serum osmolality causing release of vasopressin (antidiuretic hormone) was shifted to an abnormally low level (262 mosmol/kg H2O) in a 14-year-old girl with hypertension and signs of hypoplastic corpus callosum. There was a physiologically meaningful control of vasopressin release in response to water restriction and water load. Plasma vasopressin concentrations (range 1.2--11.9 pg/ml) were of the same magnitude as those of healthy adults, being abnormally high only when related to the hypotonicity of serum observed. Plasma concentrations of angiotensin II were higher than expected from the suppressed levels of plasma renin activity. Blood-pressure response to angiotensin II infusion was increased. Resetting of the osmostat and hypertension may both be explained by lesions of the central nervous system.