Gender differences in nighttime plasma arginine vasopressin and delayed compensatory urine output in the elderly population after desmopressin.

Purpose: Monosymptomatic polyuric nocturia is a consequence of aging. We investigated physiological differences between nonpolyuric and polyuric nocturia in the elderly population in relation to urine production regulation in young volunteers with special reference to gender.
Materials and Methods: We performed a study in 37 elderly healthy volunteers 65 years or older and 30 young healthy volunteers 20 to 40 years old who were hospitalized for 48 hours. Before admittance and during hospitalization fluid intake was standardized. The first 24 hours were at baseline conditions. On night 2 participants were given a single oral dose of desmopressin (0.4 mg). During 48 hours urine and blood samples were taken at predetermined time points to measure urine output and plasma arginine vasopressin levels.
Results: Elderly individuals with nocturnal polyuria had an inverted rhythm in urine output, which was restored after a single dose of desmopressin. There was an age related change in the circadian rhythm of arginine vasopressin secretion, which was associated with the presence or absence of nocturnal polyuria. A novel and unexpected finding was a decreased circadian rhythm of arginine vasopressin secretion in young women, similar to the pattern observed in elderly women but with a preserved decrease in nighttime urine production. Compensatory diuresis following the induction of temporary antidiuresis was markedly postponed in elderly participants.
Conclusions: Age and gender related decreased arginine vasopressin secretion at night underscores the fact that other factors modulate urine production. The pharmacodynamics of desmopressin as an antidiuretic in the elderly population are different from those in young individuals.