Urinary concentration does not exclusively rely on plasma vasopressin. A study between genders Gender and diurnal urine regulation

Aim We investigated the influence of gender on the diurnal regulation of urine production with special focus on vasopressin, oxytocin and prostaglandin E2. Methods Fifteen young women in mid‐follicular phase and 22 young men (20–33 years) were included. All participants underwent a 24‐h circadian inpatient study under standardized conditions for measurements of plasma vasopressin, oxytocin, sodium and osmolality. Urine was fractionally collected for measurements of electrolytes, aquaporin‐2 and prostaglandin E2. Results Plasma vasopressin expressed a diurnal rhythm with a night‐time increase in both genders (P