As you know, GH is supposed to rise during the night, but sleep deprivation resulted in an attenuation of GH that doesn’t rise until after sleep onset. In addition, cortisol was significantly elevated the next day, as well as catecholamines.9 If that’s not the kiss of death for maintaining an anabolic state I don’t know what is. Sleep is also critical for testosterone regulation and lack of sleep can lower testosterone levels; the total time sleeping is an important regulator as well.4
A recent study by Axelsson et al.4 examined what the most important factor regulating testosterone production during sleep was— circadian rhythms (a daily cycle of rhythmic activity based on 24-hour intervals, observed in many organisms— including us!) or total sleep. The researchers looked at traditional day workers who slept at night as well as people who worked the nightshift and slept during the day. Results of the study found that the time of day or night when the workers slept didn’t affect testosterone levels. The most important finding of the study determined that total sleep, rather than circadian rhythms, was critical for testosterone regulation. The study suggests with respect to testosterone function, that there’s a linear increase in testosterone across the sleep cycle suggesting that sleep length is critical for testosterone levels. It seems that sleep can be added to the list of factors affecting testosterone levels in addition to training level, diet and age. So the next time your boss walks in on you sleeping on the job tell him to “F**K OFF” you’re trying to get big!!

Testosterone, Circadian Rhythms and Sleep
Testosterone follows circadian rhythms or patterns during sleep. Testosterone levels increase during sleep and peak about the time of wakening in men and slowly decrease during the day.5 Interestingly the diurnal rhythm of testosterone already exists before puberty starts. One study investigated the effect of the testosterone circadian rhythm both before and after puberty. Thirty-two prepubertal and 14 pubertal boys between the ages of five and 19 years of age were studied. Diurnal rhythms of LH, FSH and testosterone were apparent in all subjects, including those aged five years old, however the average 24-hour LH and testosterone concentrations were much greater with those developing puberty.10 Testosterone levels peak at around 8 a.m. and are at their lowest around 8 p.m.6 It’s been reported that in young men, the sleep-related rise in testosterone has been linked to the first episode of rapid eye movement (REM).5 REM sleep is an active period marked by intense activity in the brain and rapid bursts of eye movements. At the same time, REM sleep is when dreaming occurs. The stimulus for testosterone production is regulated by gonadotropin-releasing hormone (GnRH), which then stimulates leutinizing hormone (LH) production from the hypothalamus (see figure 1).
During sleep, episodic bursts of LH drive testosterone production in men. The frequency and amplitude of these pulses are essential for appropriate testosterone production. There’s generally a 40-minute lag time from when the first burst of LH is secreted to stimulation of testosterone production.7 So, now you understand that during normal sleep there are episodic pulses of LH-stimulating testosterone production, however when sleep is disrupted, the circadian rhythm of testosterone is disrupted as well.

Partying Without Sleep Is Bad for Testosterone
Who the hell wants to stay home at night when you could be dancing with some hot MILF at the club?! Well, while you’re trying to “score,” the loss of sleep can be detrimental to your testosterone levels. Schiavi et al.8 reported that in a group of healthy young men, sleep deprivation causes decreases in sleep quality and REM episodes, which were associated with lower bioavailable testosterone levels, regardless of one’s age. Every bodybuilder knows he should be getting eight to 10 hours of sleep a night, but most of us take it with a grain of salt.
A single night of disrupted sleep can really take its toll on your testosterone levels. For example, when young men were exposed to a night of partial sleep loss, it resulted in a blunted testosterone response during the night. In that study when men were allowed to get a full eight hours of continuous sleep, all subjects had a nocturnal rise in testosterone. When the same subjects were allowed two hours of sleep, none of the subjects without REM sleep showed any rise in testosterone during the night.5

Another study examined testosterone levels of internal resident students in medical school. As you know, internal medical students work all hours of the night and don’t get much sleep. When the serum testosterone levels of the medical student residents were compared to other hospital personnel, the LH responses were similar, but the internal medicine residents demonstrated subnormal testosterone levels.14 Just about any occupation that doesn’t allow a good night’s sleep is going to impair testosterone production, which is especially true for new shift workers.
Shift work can wreak havoc on a person’s life during the initial adaptation period. Working at night and sleeping during the day can lead to disrupted sleep patterns, however as documented in the 2005 Journal of Clinical Endocrinology & Metabolism study, when normal sleep patterns are established there are no differences in testosterone levels between those who work at night compared to those who work during the day if they’re getting restful sleep. Axelsson et al.16 reported that low testosterone levels were found in workers who needed more sleep, had disturbed sleep/wakefulness and increased need for recovery after a work shift. The study included 62 shift workers relating how satisfied they were with their jobs, sleep quality and mood; these were then compared to the workers’ testosterone levels. Dissatisfied workers had significantly lower testosterone levels that were not related to cortisol or prolactin levels, but were associated with a greater need for sleep quality. Contrary to the dissatisfied shift workers, higher testosterone levels were found with those shift workers who were happy with their jobs and correlated with being well rested and having less disturbed sleep before their morning shifts.16