Circadian rhythm of hormones is extinguished during prolonged physical stress, sleep and energy deficiency in young men.
The circadian rhythm of hormones (N = 10) and mental performance (N = 18) was investigated in male cadets during a 5-day military training course with continuous heavy physical activities corresponding to 35% of the maximal oxygen uptake, with almost total lack of food and sleep. The 24-h means for androstenedione, dihydroepiandrosterone (DHEA), 17 alpha-hydroxyprogesterone, testosterone and thyroid-stimulating hormone decreased strongly during the course, and the circadian rhythm was extinguished below the minimum levels measured during the control experiment. The 24-h means for cortisol, dihydroepiandrosterone sulfate (DHEA-S) and progesterone increased during the course, and the circadian rhythm was abolished above the maximum levels of the control experiment. A gradual increase was found in thyroxine, free thyroxine and triiodothyronine during the first 12 h of activities, followed by a constant decrease for the rest of the course. Mental performance decreased during the course and the amplitude of its circadian rhythm increased from +/- 10% to +/- 30% of the 24-h mean. The circadian rhythms investigated were almost normalized after 4-5 days of rest. However, the nocturnal rise for cortisol, androstenedione and DHEA appeared earlier, and the plasma levels of thyroid hormones, estradiol and DHEA-S were lower during the recovery experiment than in the control experiment. The responses to stress of the circadian rhythm for mental performance and steroid hormones during the course indicate a differential regulation.
Opstad
K
K
Norwegian Defence Research Establishment, Kjeller.
D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D006728:Hormones / Q000097:blood*; D006801:Humans; D008297:Male; D008606:Mental Processes / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D012892:Sleep Deprivation / Q000502:physiology*; D013312:Stress, Physiological / Q000097:blood*; D013997:Time Factors
D006728:Hormones