Endogenous glucocorticoids exert a diverse array of physiological processes and play an important role in immune modulatory and anti-inflammatory responses. The secretion of cortisol by the adrenal gland is regulated through two mechanisms. Systemic regulation is substantiating by the hypothalamo-pituitary-adrenal axis. Furthermore, a tissue-specific local regulatory system, containing the 11?-hydroxysteroid dehydrogenase enzyme responsible for local glucocorticoid synthesis and the glucocorticoid receptor, has also been demonstrated. Based on the recent evidences, an extra-adrenal corticosteroid synthesis exists in various tissues. Steroidogenic enzymes necessary for this de novo corticosteroid synthesis have been observed in the skin, intestine, thymus and possibly in the brain, heart and lung. These locally synthesized steroids most likely act in an autocrine and paracrine manner and their regulation is mediated by local regulatory loops. The importance of this de novo corticosteroid synthesis seems to be important in the regulation of local homeostasis, immune processes and tissue-specific inflammatory reactions.
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