Role of atrial natriuretic peptide in nocturnal polyuria in elderly males

Objectives: To demonstrate nocturnal polyuria objectively and to assess the role of atrial natriuretic peptide (ANP) in healthy elderly males with and without nocturnal polyuria (NP). Patients and Methods: 31 healthy elderly men known to have NP (passing more than 33% of their 24-hour urine output d uring an 8-hour period overnight) and 12 controls without NP were invited t o take part in the study. Blood and urine samples were collected at 4-hourl y intervals in order to measure urine output, serum and urine electrolytes and osmolality as well as serum cortisol, renin, aldosterone, arginine vaso pressin (AVP) and ANP, Results: 26 men with NP and 8 controls agreed to tak e part in the study. Subjects with NP were found to have a diuresis and nat riuresis as well as a significant increase in ANP overnight compared to the control group. There was no difference in the other parameters between the 3 groups, with the exception of aldosterone and AVP, Conclusions: This stu dy has shown a group of subjects with increased natriuresis and diuresis ov ernight, associated with an increase in ANP. It is possible that subclinica l cardiac failure causes an increase in ANP therefore causing nocturnal uri nary symptoms and this theory needs further exploration.