One-step synthesis of a cortisol derivative for radioiodination and application of the 125I-labeled cortisol to radioimmunoassay.

Abstract
A one-step synthesis of a cortisol derivative for radioiodination is presented. The radioimmunoassay for cortisol using the bridge heterologous 125I-labeled antigen was more sensitive than that using a bridge homologous antigen. Cortisol levels in saliva and serum were easily determined by direct radioimmunoassay with the proposed 125I-labeled antigen.