ADRKNOCORTICAL FUNCTION AND CORTISOL METABOLISM IN OLD AGE*

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Abstract
In this study the influence of old age on adrcnocortical function and cortisol metabolism was investigated, along with renal, hepatic and thyroid function in 15 young men (25–40 years old) and 50 old men (60–96 years old). By the criteria of 8-a.m. plasma levels of free and conjugated 17-hydroxycorticosteroids (17-OH-CS) and the plasma corticoid response to ACTH stimulation, no significant change in adrenocortical function could be demonstrated with advancing age. However, there was a progressive and significant decrease in the urinary excretion of 17-OH-CS with aging. Following intravenous administration of a standard dose, cortisol disappeared from the circulation at a significantly slower rate in the old men. The maximal levels of plasma conjugated 17-OH-CS observed after cortisol infusion were statistically the same for all ages, but the rate of decay from peak values was slower in the older subjects. These alterations in cortisol metabolism were associated with a significant increase in the level of blood urea nitrogen and bromsulfalein retention, and a significant decrease in endogenous creatinine clearance and basal metabolic rate. The plasma protein-bound iodine level and thyroidal uptake of I131 were unaffected by aging. A combination of decreased cortisol catabolism by the liver and other tissues and an impairment in the renal excretion of cortisol metabolites is proposed to explain these observations. The thyroid gland does not appear to be involved.

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