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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
Another interesting finding was that the sole predictor of morning testosterone was the workers’ quality of sleep. Having sufficient sleep was more predictive of testosterone levels than age, BMI and smoking. In addition to being sleep deprived from work, many sleep disorders can decrease testosterone levels. Sleep quality is affected by many breathing-related disorders such as sleep apnea, which has been shown to affect approximately four percent of middle-aged men.17
Sleep Apnea Suppresses Testosterone Production!
Sleep apnea happens during sleep when there’s a cessation of airflow that occurs for at least 10 seconds (usually 20 to 30 seconds, but rarely greater than two minutes). Apnea is accompanied by snoring, sleep arousals and hypoxia. The term sleep apnea describes two major sleep-related clinical problems: obstructive sleep apnea and central sleep apnea.
Central apnea is caused by neurochemical stimulation, which can result in impairment of respiratory control of breathing. Obesity is often a factor, but not all patients with central sleep apneas are obese. Approximately 18 to 40 percent of affected patients are no more than 20 percent heavier than their ideal bodyweight.
Obstructive apnea is caused by upper airway obstruction at the level of the pharynx and is the most common form of sleep apnea. What should concern bodybuilders is that a large neck circumference (collar sizes greater than 17.5 inches) has been associated with sleep apnea. Obesity is a major contributing factor to sleep apnea as the excess adipose tissue around the neck collapses the trachea during sleep. Sleep apnea results in a reduction in both LH and testosterone levels. Lubo****zky et al.17 examined healthy young men and compared them to overweight sleep apnea patients and found that sleep apnea resulted in severe testosterone dysfunction. Compared to healthy young men, sleep apnea patients had lower total LH and testosterone levels due to decreased LH pulse amplitude and decreased pulsatile testosterone secretions during the night. When obese patients lose weight, the nightly circadian rhythms of LH and testosterone are restored.19
Obesity in itself suppresses testosterone levels, but the hypoxia that occurs during apnea suppresses testosterone levels as well. Additionally, when apnea patients are placed on nasal continuous positive airway pressure (CPAP) machines (which delivers air into your airway through a specially designed nasal mask), testosterone levels revert back to normal, demonstrating that obesity alone isn’t the sole cause of decreased testosterone levels occurring during sleep.20
When patients with sleep apnea were compared to each other, the degree of testosterone suppression taking place with sleep apnea was directly related to the amount of hypoxia occurring during sleep. Decreased morning testosterone levels, but not LH, is related to the degree of hypoxia.20 For example, Kouchiyama et al.31 found that when sleep apnea patients were compared to each other, the patients who had less severe oxygen saturation had testosterone peaks at 6 a.m., whereas the patients who were classified as having severe oxygen desaturation during sleep exhibited delayed peaks in testosterone for example, at 10 a.m.
Test Replacement Isn’t a Cure for Apnea
One might think that giving testosterone to sleep apnea patients would result in lifestyle enhancement, but testosterone itself has been linked to sleep apnea. Testosterone is the only androgen that has been attributed to control of breathing, although its role is unclear.
In a study of seven obese men, all but the hypogonadal man had nocturnal hypoxemia or sleep-disordered breathing.34 In relation to sleep-disordered breathing, two randomized, placebo-controlled studies in older men are available and document that high-dose testosterone administration worsens sleep and breathing, although lower dose, steady-state testosterone delivery may be less likely to do so.30 Testosterone alters neurochemical control of breathing and administration of testosterone to hypogonadal men results in disturbed breathing patterns.21 Older men given high doses of testosterone resulted in reduced sleep time (approximately one hour) and disrupted breathing during sleep. So how is this happening? The author concluded that even though testosterone increased lean muscle mass and reduced fat mass, the disruption in sleep could have been attributed to the fact that testosterone administration changes nocturnal metabolism, potentially impairing sleep quality. In addition, the large rapid increases in lean mass reflect changes in tissue hydration, which could cause edema in the airways, disturbing breathing.30 Another possible cause of the increased number of sleep disturbances, which can occur with testosterone administration, is that testosterone decreases melatonin production. Patients with GnRH deficiency who have low levels of testosterone have higher levels of melatonin than normal controls. The administration of testosterone enanthate to GnRH patients resulted in a reduction in melatonin to the levels appropriate for age-matched controls.33 What’s interesting is that the pineal gland where melatonin is secreted has the ability to take up and metabolize estradiol and testosterone.32


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