title: The cortisol fluctuations in plasma in relation to human regulatory nonshivering thermogenesis.
abstract: It is known that many stressful situations are accompanied by an increase in plasma cortisol concentration. This study was undertaken to see if a standardized and moderate exposure to cold under simultaneous peripheral vasodilation, which is known to result in increased oxygen consumption and plasma concentration of noradrenaline, can be considered a stress, based on changes in plasma cortisol concentration. Since the nonshivering thermogenesis induced is dependent on normal thyroid function, nine of the 19 adult humans exposed to cold were normo-, four hyper-, and six hypothyroid. The cold exposure was carried out in every case between 9 a.m. and 11 a.m. Since the cortisol secretion reflects the circadian cycle, a further six normothyroid persons were exposure to cold between 5 a.m. and 7 a.m. The exposure in this study does not reflect any stress condition, as the plasma cortisol concentration during the investigations between 9 a.m. and 11 a.m. decreased significantly by mean values of 0.1 mmol/l (29%) (range: -0.07--0.2 mmol/l) in the normothyroid group, by 0.23 mmol/l (68%) (range: 0.09--0.44 mmol/l) in the hyperthyroid group, and by 0.16 mmol/l (29%) (range: 0.03--0.38 mmol/l) in the hypothyroid group. The normothyroid persons investigated between 5 a.m. and 7 a.m. showed a significant fall similar to that mentioned above. The differences in the results obtained between the normo- and dysthyroid groups, before and during the exposure, merely reflected variations known from non-stressful conditions.
mesh_terms: D000328:Adult; D001833:Body Temperature Regulation; D003080:Cold Temperature; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D006980:Hyperthyroidism / Q000097:blood*; D007037:Hypothyroidism / Q000097:blood*; D008297:Male; D008875:Middle Aged; D013312:Stress, Physiological / Q000097:blood*
chemical_list: D006854:Hydrocortisone