RESUMO
OBJECTIVE: To delineate the role of antidiuretic hormone (ADH) in relation to nocturnal polyuria, and to identify the factors influencing on the diurnal antidiuretic hormone level. METHOD: The ADH was measured by radioimmuoassay at daytime (2:00 PM) and at nighttime (2:00 AM) with nocturnal polyuria group (11) and without nocturnal polyuria group (8). Urine volume, serum osmolarity, urine osmolarity, and blood pressure were also measured at the same time. RESULTS: 1) The ADH at 2:00 AM did not increase in nocturnal polyuria group, although it increased in no-symptom group. 2) There was a statistically significant correlation between wheelchair ambulation time and daytime ADH level. 3) The difference of ADH level between daytime and nighttime showed decrease in orthostatic hypotension group. CONCLUSION: There was relationship between nocturnal polyuria and diurnal variation of ADH level. The ADH concentration seems to be influenced by the postural factors and sympathetic factors.