Factors impacting on the action of glucocorticoids in patients receiving glucocorticoid therapy.

Glucocorticoids (GCs) are steroid hormones, which are essential for life. They are secreted by the adrenal cortex under the control of the hypothalamic-pituitary-adrenal (HPA) axis. Glucocorticoids are essential for the normal function of most organ systems and, in both, excess and deficiency can lead to significant adverse consequences. Adrenal insufficiency (AI) is a rare, life-threatening disorder characterized by insufficient production of corticosteroid hormones. Primary AI is defined by the inability of the adrenal cortex to produce sufficient amounts of glucocorticoids and/or mineralocorticoids despite normal or increased adrenocorticotropin hormone (ACTH). Secondary AI is adrenal hypofunction due to insufficient amount of ACTH produced by the pituitary gland. Conventional treatment of both primary and secondary adrenal insufficiencies involves lifelong glucocorticoid replacement therapy. The role of cortisol deficiency and the impact of hydrocortisone replacement on morbidity and mortality in this patient group are under increasing scrutiny. Established glucocorticoid replacement regimens do not completely mirror endogenous hormonal production, and their monitoring to ensure optimum therapy is hampered by the lack of reliable biomarkers of hormone sufficiency. A further confounding issue is the tissue-specific regulation of glucocorticoid through the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) with research focusing on the role of this prereceptor regulation in the development of adverse metabolic features in patients. This review defines the factors influencing glucocorticoid action in patients with adrenal insufficiency receiving glucocorticoid therapy.