Neuroendocrine response to supine posture in healthy children and patients with nocturnal enuresis.

OBJECTIVE

To elucidate the background behind the attenuated circadian rhythm of vasoactive hormones in patients with nocturnal enuresis, we tested the hypothesis that enuretic children exhibit an abnormal neuroendocrine response to a baroreflex stimulus during daytime.

METHODS

In fifteen children and adolescents (aged 13.4 +/- 0.9 years) with severe nocturnal enuresis and 10 age- and sex-matched healthy controls, we performed a 'daytime supine posture' (DSP) study at 10:00 h.

METHODS

Blood was sampled for measurements of plasma vasopressin (P(AVP)), angiotensin II (P(ANGII)), atrial natriuretic peptide (P(ANP)) and serum aldosterone (S(ALDO)), and mean arterial blood pressure (MAP) and heart rate (HR) were measured during the study.

RESULTS

In both controls and patients with enuresis, DSP at 10:00 h resulted in a marked fall in MAP and HR, a rise in pulse pressure (PP) and estimated plasma volume (PV) and a significant suppression of P(AVP), P(ANGII) and S(ALDO), whereas P(ANP) increased. There were no significant differences between groups in haemodynamic or neuroendocrine responses to DSP.

CONCLUSIONS

The study showed that children with nocturnal enuresis exhibit a normal neuroendocrine response to supine posture during daytime indicating that baroregulatory mechanisms per se are not playing a significant pathogenic role. Interestingly, the normal neuroendocrine response to supine posture seems to undergo marked circadian changes, as supine posture at night-time is associated with increased levels of vasoactive hormones.