Diurnal plasma vasopressin and urinary output in adolescents with monosymptomatic nocturnal enuresis.

Plasma arginine vasopressin (AVP) levels, urinary flow and urine osmolality were investigated in a group of adolescents (20 boys and 5 girls), aged 11-21 y, with severe monosymptomatic nocturnal enuresis and a control group of healthy adolescents (16M and 4F) with similar age- and sex-distribution. Half of the control group was investigated twice, with an interval of 6 months. AVP samples were taken every fourth hour in all adolescents and half of the control group were also investigated every second hour to achieve more samples during controlled sleep. After the study the enuretic group were put on long-term oral desmopressin (DDAVP). The difference between day and night values of AVP was significant for both groups, but there was no difference in the day/night ratios of plasma-AVP. All the adolescents produced less urine while asleep, but the controls produced significantly more urine than the enuretics during day. The controls also had a significantly larger nocturnal elevation of urine osmolality than the enuretics, thus a tendency towards polyuria was found. We could not find any significant difference between responders to DDAVP treatment and non-responders in any of the parameters studied. AVP is secreted in a pulsatile fashion and with point hormone samples taken every fourth or second hour we were unable to find any difference in the diurnal AVP secretion between enuretics and normal controls.