THE DIURNAL VARIATION OF PLASMA LEVELS AND URINARY EXCRETION OF 17-HYDROXYCORTICOSTEROIDS IN NORMAL SUBJECTS, NIGHT WORKERS AND BLIND SUBJECTS*†

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Abstract
A diurnal rhythm in the levels of plasma 17-hydroxycorticosteroids of normal subjects was shown. A maximum value was regularly seen during the later hours of sleep (5-8 A.M.), usually near 6 A.M. From 8 A.M. to midnight the levels followed a downward trend, the decrease being more rapid in the first few hours after the peak. Between 2 A.M. and 6 A.M. the concentrations rose rapidly. 17-Hydroxycorti-costeroid excretion in urine followed the same general curve of variation as that of plasma, but was delayed about 2 hours. Night workers and blind had the same diural variation as the normal subjects. In normal subjects and in the night workers plasma iron concentrations manifested a periodicity like that of 17-hydroxycorticosteroids, but the cycle was not so definite in the blind individuals. An inverse cycle seemed to exist in concentrations of eosinophils, but individual variation was so great that there is a considerable degree of statistical uncertainty as to the significance of the variations.