Abstract
Competitive protein binding (CPB) analysis has yielded an easy and sensitive means for the determination of the steroid hormones in body fluids. We have measured the plasma total corticosteroid (total CS) by the modified Murphy's method, and have developed the simple determination method for plasma 11-deoxycorticosteroid (deoxy CS). Deoxy CS was extracted with a 1: 2 mixture of chloroform and carbon tetrachloride, followed by partition against 3 volumes of water 3 times. The present method requires only one tube for the whole procedure. The recovery rate of the extractioning through partitioning is 66% for 11-deoxycortisol and 4.9% for cortisol. The acuracy of the method is satisfactory, the coefficient of variation is 6-7%. In this method the interference of the steroids other than deoxy CS can not be excluded completely, therefore, the application of this method is limited.
We applied this technique for the evaluation of pituitary ACTH reserve following the overnight administration of metyrapone. After giving each 750mg of metyrapone at 8p. m., 12 midnight and 4a. m., the plasma level of total CS and deoxy CS in normal subjects rose to 10μg/dl or more; on the other hand, in the patients with the impaired ACTH reserve the plasma CS level remained less than 8μg/dl. The deoxy CS value after the overnight metyrapone showed the more distinct difference between normal subjects and the patients with the impaired ACTH reserve. In order to confirm the effect of metyrapone, the additional metyrapone was administered to the patients on one day regular schedule. The plasma CS level did not differ significantly after the one day metyrapone administration. We consider that the overnight metyrapone test with plasma CS measured by CPB method is adequate for the routine clinical use.
