Interrelation of Iodide Clearance and Adrenocortical Activity

Abstract

Studies of the circadian patterns of variation of radiodide excretion, creatinine excretion and clearance and plasma 17-hydroxycorticosteroid concentration have been conducted in healthy volunteer euthyroid subjects. The diurnal patterns of change in these indices were generally similar. Early morning oral administration of 50 mg hydrocortisone acetate reversed the parallel pattern of change in radioiodide excretion and plasma 17-hydroxycorticosteroid observed on the control day and produced significant and parallel increments (when compared to control values) in early morning radioiodide excretion and plasma 17-hydroxycorticosteroid concentration. Parallel, although statistically insignificant, changes in creatinine, sodium and chloride excretion were also observed. Ammonium chloride and dextran loading produced dissociation of the excretion patterns of sodium and chloride from those of creatinine and radioiodide. Acute intravenous hydrocortisone loading significantly increased creatinine and radioiodide clearances as well as sodium and chloride excretion rates; a statistically significant correlation between the increments in creatine clearance and in radioiodide clearance was observed. These observations have suggested that the circadian pattern of renal radioiodide clearance may be due, at least in part, to variations in glomerular filtration induced by the circadian pattern of adrenal corticosteroid secretion.