Influence of nocturnal oxygen desaturation on circadian rhythm of testosterone secretion

To investigate the influence of nocturnal oxygen desaturation on the circadian rhythm of testosterone secretion, polysomnography was performed on 2 consecutive nights in 24 male subjects who complained of loud snoring and/or obesity. During the first night, we collected blood samples every 4 h via a catheter and measured serum testosterone. We arbitrarily defined severe oxygen desaturation as that exceeding the baseline SaO2 by 4% during 80 min of total sleep time. The subjects were divided into 2 groups from the data of the second night; one was the severe desaturation group as mentioned above, and those who suffered less desaturation were classified as the free to mild oxygen desaturation group. We found that in the latter group peak testosterone levels appeared at 6 a.m. On the other hand, the severe desaturation group exhibited delayed peak testosterone levels, i.e. at 10 a.m. We calculated the ratio of the testosterone level at 10 a.m. to that at 6 a.m., and found a significant correlation between this ratio and total desaturation time (r = 0.446, p less than 0.05). These data suggest that severe oxygen desaturation may alter the circadian rhythm of testosterone secretion.