Plasma osmolarity was 255 mOsm/kg H2O, while urinalysis revealed a urinary Na level of 87 mEq/L and urinary osmotic pressure of 691 mOsm/kg H2O. The serum ADH level was 1.6 pg/mL, suggesting that inappropriate secretion of ADH was responsible for the excessive excretion of sodium and hypotonic hyponatremia. Here, AVP is linked to Hyponatremia.