Competitive protein binding radioassay of plasma and urinary unconjugated cortisol.

In order to establish a more reliable profile of the function of the adrenal cortex, a study has been made of this simultaneous estimation of plasma and urinary unconjugated cortisol by competitive protein binding (CPB) radioassay. Both plasma and urinary cortisol were measured by CPB radioassay after solvent extraction. Normal ranges were found for plasma and urinary cortisol. The samples obtained in the morning (8:00 am) established a normal plasma cortisol range of 9.0-21.6 mug% with a mean of 15.3. range for urinary unconjugated cortisol was 12.0-41.5 mug/day (mean 26.9). Dexamethasone suppression and adrenocorticotrophic hormone stimulation of plasma and urinary cortisol were tested with individuals having normal and abnormal adrenal cortical function. RESULTS INDICATED A GOOD CLINICOPATHOLOGICAL CORRELATION. It was concluded that plasma and urinary unconjugated cortisol are reliable laboratory tests for adrenocortical function and would be the methods of choice rather than urinary 17-ketogenic steroids.