Association of Increased Nocturnal Urine Volume with a Gonadotropin- Independent Reduction of Nighttime Serum Testosterone Level in Male Nocturia Patients

Abstract

Nocturia is common in the aging male. One factor is an increased nocturnal urine volume. However, the reasons for the increased urine amount in the night remain unclear. Sex steroid hormone has been found to play a role in the regulation of water/solute excretion. It would be valuable to know whether there is any correlation between androgen status and nocturnal urine production in men with nocturia. The study included 22 male patients (mean age 75.6 ± 6.2) with nocturia (＞2 micturition per night). All of them maintained a voiding diary and collected urine for 3 successive days. Samples of urine collected separately at daytime and nighttime were sent for assay of sodium and calcium. Serum samples at 7 am and midnight were collected for determination of testosterone, luteinizing hormone (LH), atrial natriuretic peptide (ANP) and aldosterone with radioimmunoassay. We correlated the ratio of nocturnal urine volume over 24 h urine volume (N/W) with various parameters using Pearson's correlation test. Patients void 4.6 ± 2.1 (range 2.0-9.5) times per night. The ratio of nocturnal urine volume ranges from 0.22 to 0.69, with a mean of 0.43. There is a significant positive correlation between nighttime sodium excretion and the ratio of nocturnal urine volume, while excretion of calcium, either in daytime or in nighttime, does not have significant correlation. Interestingly, patients with higher ratio of nocturnal urine volume have lower serum testosterone level in the midnight, while it does not have significant correlation in the morning. Serum LH level, either at 7 am or at midnight, shows no significant correlation with the ratio of nocturnal urine volume. Increased ANP and aldosterone were seen associated with increased N/W. This study shows that the increased nocturnal urine excretion is mainly due to an increased nighttime sodium excretion and is associated with a gonadotropin-independent reduction of serum testosterone level. Future studies are required to determine the significance of and causes for the decreased nighttime serum androgen level in male patients with nocturnal polyuria.