The aim of this study was to test the hypothesis of an association between hypothalamic-pituitary-adrenal (HPA) axis reactivity and progression of periodontal disease. Histocompatible Lewis and Fischer 344 rats respond to stressful stimuli with low and high HPA axis reactivity, respectively. Experimental periodontitis was induced by tying a silk ligature around the neck of maxillary 2nd right molar teeth in 10 Lewis and 10 Fischer 344 rats with contralateral non-manipulated teeth as controls. Twenty non-manipulated animals were included. Also, experimental periodontitis was induced in 10 adrenalectomized Wistar rats and in 10 sham-operated rats. Furthermore, corticosterone pellets were subcutaneously implanted in 9 Lewis rats, while placebo pellets were implanted in 8 animals. Disease progression was evaluated histometrically and radiographically. The low-responding Lewis rats developed significantly less periodontal breakdown than did the high-responding Fischer 344 rats. Administration of corticosterone increased the disease development. while adrenalectomy reduced the disease severity. Our findings demonstrate the importance of genetic factors in the development of periodontal disease, and suggest that HPA axis hyper-activation is one mechanism by which periodontal disease susceptibility may be increased.

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.

Female cadets maintained a significantly more fat-predominant fuel metabolism than did male cadets in response to sustained exercise and semistarvation.