Measurement of Corticosteroid-Binding Globulin in Man

Abstract

A method for quantitation of corticosteroid-binding globulin (CBG) has been developed utilizing gel filtration and 4-¹⁴C cortisol. With this method it was demonstrated that exchange equilibrium was essentially instantaneous at 37 C but that 2–4 hr were required at 4 C. Cortisol was demonstrated to exert a protective effect against destruction of binding by heating to 60 C. Increase in binding with decrease in assay temperature was again demonstrated for normal and pregnancy serum utilizing the present method. Values in 19 normal males ranged from 23 to 45 mg/l of plasma (35±3.6). No significant difference was found in 16 normal females (mean 33±4.2 mg/l), and these values were in close agreement with the results reported by us previously after direct isolationof CBG from normal plasma. Pregnant females had a significant increase in CBG by the second month and reached an elevated plateau value of 73 mg/l by the sixth lunar month. Patients with cancer of the prostate given 5 mg diethylstilbestrol daily had no change at 24 hr, a significant rise at 48 hr, and reached an elevated plateau value (mean 92 mg/l) by 7 days. Patients with cirrhosis of the liver had a significant decrease in CBG (mean value 23 mg/l) as did patients with hypoalbuminemia of varying etiologies. Patients with cancer of the lung and hyperresponsiveness to ACTH had a slight, but significant, elevation in CBG. Normal values were found in adrenal insufficiency, hypopituitarism, hyper- and hypothyroidism, hypogonadism (males), acromegaly, and in Cushing–s syndrome due to adrenocortical hyperplasia, adrenal adenoma, and “oat-cell” carcinoma of the lung.