A large number of physical and psychological stresses have been shown to increase adrenocortical secretion. The evidence for this statement has chiefly consisted in demonstrating increased plasma hydrocortisone levels, increased urinary excretion of hydrocortisone metabolites such as hydroxycorticoids and 17-ketosteroids, and increased responsivity to corticotropin (ACTH) in subjects under the disturbing condition. Such procedures do not permit a quantitative estimate of the production rate of the hormone; at best they merely indicate that hormone production has been increased. Within the past decade, a number of techniques have been developed for quantitative assessment of hormone production. Three basic methods are currently available for the determination of hydrocortisone production: (1) kinetic studies employing the radioinert hormone, (2) kinetic studies employing radioactive hormone turnover, and (3) isotope dilution, also using the radioactive hormone.
The first method utilizes a differential equation proposed by Samuels1
HAROLD PERSKY. Introduction and Removal of Hydrocortisone from PlasmaRates in Normal Subjects and Anxious Patients. Arch Gen Psychiatry. 1962;7(2):93–97. doi:10.1001/archpsyc.1962.01720020017003