Urinary Excretion of Antidiuretic Hormone Under Various Hydration States in Man

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 of ADH/day (12.9 ±2.0 µU/ml) (mean±s.E.), and less than 8.2 mU/day (2.0 µU/ml), respectively. 8 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/hr (137.9± 33.4 µU/ml) (mean±s.E.) in 9 normal subjects. At that time, plasma and urine osmolality increased to 282.5±1.1 and 1004±43 mOsm/kg (mean±s.E.), 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 (mean±s.E.) after water deprivation. In 9 normal subjects, urinary ADH excretion decreased after water loading from 3.0±0.5 mU/hr to below 0.6 mU/ hr (0.6 µU/ml) with a concurrent reduction of plasma and urine osmolality to 274.8±1.4 and 81±7 mOsm/kg (mean±s.E.), respectively. Two types of daily urinary excretion patterns of ADH 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, either case showed no suppressibility of ADH in the face of an expansion of body fluid with hypo-osmolality of the plasma. © 1978, Tohoku University Medical Press. All rights reserved.