Disruption of the nocturnal testosterone rhythm by sleep fragmentation in normal men

Recently, we have demonstrated that in normal men the nocturnal testosteron e rise antedated the first rapid eye movement (REM) sleep episode by about 90 min and was correlated with REM latency. To further elucidate whether th e diurnal testosterone rhythm is a sleep-related phenomenon or controlled b y the circadian clock, we determined serum testosterone levels in 10 men du ring the ultrashort 7/13 sleep-wake cycle paradigm. Using this schedule, su bjects experienced partial sleep deprivation and fragmented sleep for a 24- h period. Serum testosterone levels were determined every 20 min between 19 00-0700 h with simultaneous sleep recordings during the 7-min sleep attempt s. The results were compared with those obtained in men during continuous s leep. Although mean levels and area under the curve of testosterone were si milar in both groups, fragmented sleep resulted in a significant delay in t estosterone rise (03:24 h +/- 1:13 vs. 22:35 h +/- 0:22). During fragmented sleep, nocturnal testosterone rise was observed only in subjects who showe d REM episodes (4/10). Our findings indicate that the sleep-related rise in serum testosterone levels is linked with the appearance of first REM sleep . Fragmented sleep disrupted the testosterone rhythm with a considerable at tenuation of the nocturnal rise only in subjects who did not show REM sleep .