Urinary excretion of antidiuretic hormone under various hydration states in man.

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Abstract
In order to clarify the physiological role of antidiuretic hormone (ADH) in regulating the renal water handling, a bioassay for ADH in urine was devised, and urinary excretion of ADH was determined in 21 normal subjects, 14 patients with central diabetes insipidus and 8 patients with inappropriate secretion of ADH (SIADH). Under normally hydrated states, 12 normal subjects and 7 patients with central diabetes insipidus excreted 22.9 .+-. 3.2 mU [units] of ADH/day (12.9 .+-. 2.0 .mu.U/ml) (mean .+-. SE), and less than 8.2 mU/day (2.0 .mu.U/ml), respectively. Eight patients with SIADH excreted ADH ranging from 15.6 to 808.2 mU/day. Under dehydrated states, ADH excretion increased to 3.0 .+-. 0.5 mU/h (137.9 .+-. 33.4 .mu.U/ml) in 9 normal subjects. At that time, plasma and urine osmolality increased to 282.5 .+-. 1.1 and 1004 .+-. 43 mOsm[osmolal]/kg, respectively. In all of 7 patients with central diabetes insipidus, urinary ADH could be detected when plasma osmolality increased to 298.4 .+-. 1.7 mOsm/kg after water deprivation. In 9 normal subjects, urinary ADH excretion decreased after water loading from 3.0 .+-. 0.5 mU/h to below 0.6 mU/h (0.6 .mu.U/ml) with a concurrent reduction of plasma and urine osmolality to 274.8 .+-. 1.4 and 81 .+-. 7 mOsm/kg respectively. Two types of daily urinary ADH excretion patterns were found in patients with SIADH. One of them had ectopic ADH producing tumor and excreted a relatively large amount of ADH, and the other was a non-tumor case which excreted a normal amount of ADH. However, neither case showed suppressibility of ADH in the face of body fluid expansion with hypo-osmolality of the plasma.