Protein-binding assays for adrenocorticoids

The measurement of the adrenocortical hormones, Cortisol and corticosterone, m blood plasma has previously best been done by procedures employing varying degrees of purification of the hormone, followed by photometric or fluorimetric quantitation. These methods have been relatively difficult or laborious, particularly in the case of the procedures that most specifically measure the hormoneof intent. These limitations are considerably overcome by new assays for Cortisol and corticosterone based on the principle of competitive protein-binding of the steroids in the presence of radioactively labeled steroid of the same molecular species. These methods are described and data on the specificity of such a method for corticosterone are presented and compared with one of the better fluorimetric assays.