Decrease in nocturnal urinary levels of arginine vasopressin in patients with nocturnal polyuria.

OBJECTIVES

To elucidate whether heart function and endocrine levels of arginine vasopressin (AVP) or solute diuresis is associated with the nocturnal voided volume, and whether the urinary AVP could be a parameter for screening for nocturnal polyuria caused by AVP insufficiency.

METHODS

A total of 50 patients were enrolled in this study. The blood and urine samples were obtained every 6 hours at 6 pm, 12 am, 6 am, and 12 pm. Atrial natriuretic peptide and brain natriuretic peptide were measured at admission. All voided urine samples were collected every 6 hours for examination. The evaluation items were AVP, osmolarity, sodium, potassium, chloride, and creatinine in blood and urine.

RESULTS

The patients were classified into a group with nocturnal polyuria (n = 21) and a group without nocturnal polyuria (n = 25). There was no significant difference in atrial natriuretic peptide, brain natriuretic peptide, electrolytes in blood and urine, and plasma AVP of each sample between the two groups, but urinary AVP/urinary creatinine and urine osmolarity at 12 am and 6 am in the group with nocturnal polyuria were significantly lower than those in the group without nocturnal polyuria. The nocturnal voided volume correlated with urinary AVP/urinary creatinine level in the urine samples obtained at 12 am and 6 am.

CONCLUSIONS

The present data have demonstrated that the significant decrease in urinary AVP/urinary creatinine level at 6 am may contribute to the increased nocturnal voided volume followed by nocturia and that the circadian rhythm disorder of AVP can be predicted by a noninvasive test measuring urinary AVP/urinary creatinine in the urine voided early in the morning.