[Clinical assessment of posterior pituitary function by measurement of unextracted random urine]

To evaluate posterior pituitary function without any provocative examination, vasopressin (AVP) concentrations of random urine were measured by high-sensitive radioimmunoassay (AVP-RIA Kit, Mitsubishi Petrochemical Co., Ltd.). No apparent interference for the AVP measurement in unextracted urine was seen after appropriate dilution of urine sample. Urinary AVP did not degenerate at least for 24 hr at room temperature. AVP concentration of random urine was significantly correlated with AVP excretion in 24hr-urine in normal subjects. In 25 patients with neurogenic diabetes insipidus diagnosed by hypertonic saline infusion test, the AVP concentration in random urine was less than 13 pg/mg Cr. In approximately 1% of the normal subjects the urinary AVP level was below this range. Therefore, more intensive examinations should be planned to rule out the failure of AVP secretion in the case of such low AVP level in random urine. We also investigated the physiological changes in AVP secretion in 815 children and 352 pregnant women by measurement of urinary AVP. Even a large number of samples could be measured using this simple procedure.