When given in adequate amounts, the therapeutically and metabolically active adrenal 17-hydroxycorticoids (17-OHCS) suppress the activity of the normal pituitaryadrenal axis. This is accomplished not by a direct action upon the adrenal cortex but by suppressing endogenous secretion of pituitary corticotropin (ACTH). This effect occurs to only a slight degree with a pure mineralocorticoid, such as desoxycorticosterone, but is marked with all of the adrenal corticoids used for systemic treatment, such as cortisone, hydrocortisone, prednisone, and prednisolone.
The first consequent of suppression of endogenous corticotropin secretion by exogenous corticoid is a marked diminution in the secretion of hydrocortisone, corticosterone, and adrenal androgens by the adrenal cortex; apparently diminution in aldosterone secretion is less pronounced. If adequate doses of exogenous steroid are given for long periods, the adrenal cortex slowly involutes and becomes atrophic. Accompanying this anatomic decrease in mass is a physiologic loss of sensitivity to stimulation, characterized by a
YOUNG II, De FILIPPIS V, MEYER FL, WOLFSON WQ. Maintenance of Adrenal Cortical Responsiveness During Prolonged Corticoid TherapyEvaluation of Intermittent Administration of Repository Corticotropin Injection. AMA Arch Intern Med. 1957;100(1):1–10. doi:10.1001/archinte.1957.00260070015001