Circadian rhythm of the plasma cortisol level in cases of prolonged coma.

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Abstract
Circadian variations of plasma cortisol were studied in 4 different groups of subjects; 17 patients with prolonged coma, 3 patients with tetraplegia with alert consciousness and without body movement, 4 patients with stabilized chronic infection with alert consciousness and with normal body movement, and control subjects consisting of 7 healthy volunteers and 5 patients with various neuromuscular diseases without disturbance of consciousness, motor dysfunction or infection. The maximum level of plasma cortisol attained during the circadian variations was low in prolonged coma, whereas the minimum level was high in prolonged coma, as compared to other 3 groups. The amplitudes between the maximum and the minimum level were significantly lower in prolonged coma than in controls (P < 0.005). The tendency for the maximum level to appear at early morning and the minimum at late evening was similarly observed in both prolonged coma and control groups suggesting that there is no phase shift of the circadian rhythm of cortisol in prolonged coma. The responses of plasma TSH [thyrotropin] to synthetic TSH[thyrotropin]-releasing hormone or those of plasma cortisol to ACTH were not different between prolonged coma and control groups, suggesting that the reduced amplitude in prolonged coma is not attributed to the function of the patients'' pituitary and/or adrenal cortex. There were no differences in diurnal variations in plasma glucose or non-esterified fatty acid between the prolonged coma and control groups. Nevertheless the former was fed with liquid food via a nasal tube. Highly significant reduction of the amplitude of circadian variation of cortisol in prolonged coma may not be due to exogenous factors, such as a decreased body movement, complications due to chronic infection, or tube feeding. The results seem to suggest that the reduced amplitude of the circadian variations in plasma cortisol may be related to the unconsciousness of prolonged coma due to severe damage to the CNS.

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