Biological assays of cortical hormone and their application

Studies on the adrenal cortex began with the demonstration that it is essential for life. The next step was the demonstration that within the gland some substance or substances are present which can be extracted and used in substitution therapy. This was followed by fractionation of adrenocortical extracts and the isolation of crystalline steroids. With the help of these extracts and steroids it became possible to establish a vast body of knowledge concerning the rate of secretion of cortical hormone, their metabolic effects, metabolism, urinary excretion and other physiological data concerning the adrenal cortex. In all these studies, especially in the earlier ones, biological assays, whether used in a qualitative or a quantitative manner, have played the most prominent, if not the only, role in obtaining such information