Physical examination and laboratory findings (urine sodium concentration < 10 mEq/L, urine osmolality 775 mOsm/kg, fractional excretion of major solutes FENa, FEUrea, and FEUA) suggested that a decrease in extracellular fluid due to a decrease in dietary intake and extrarenal sodium loss were more likely than syndrome of inappropriate antidiuretic hormone secretion.[25] The elevated antidiuretic hormone level (24.91 pg/mL) was suspected to contribute to the development of osmoregulation for hypovolemia. This evidence concerns the gene AVP and Down syndrome.