Circadian rhythm in the elderly: a study using a cortisol-specific radio-immuno-assay

Plasma cortisol levels and diurnal variation have been examined in 30 elderly patients and compared with a control group of 29 middle-aged healthy subjects. The elderly patients had normal plasma cortisol levels which exhibited the diurnal variation seen in the younger age group. In spite of microscopic degenerative changes in the adrenals with age their secretory function and response to hypothalamic pituitary stimulation appear to remain normal.