ABSTRACT
I. HISTORICAL OVERVIEW The term glucocorticoid derives from early observations that these hormones were involved in glucose metabolism. They stimulate several processes that collectively serve to increase and maintain normal concentrations of glucose in the blood. The influence of glucocorticoids (GC) on the immune system has been recognized for more than half a century. Before the discovery of GC as hormonal substances produced by the adrenal cortex, morphological manifestations of the regulation of lymphoid tissues were extensively studied. Experimental manipulations such as adrenalectomy led to thymic hypertrophy in rats, as reported by Jaffe in 1924 [1]. Conversely, exposure of rats to various types of stress induced, apart from adrenal enlargement, thymus involution. The magnitude of these effects was much less pronounced in adrenalectomized or hypophysectomized animals [2], which demonstrated that the pituitary-adrenal axis can act as a functional link between the central nervous and immune systems. Going one step further towards identification of potential agents responsible for these effects, it was subsequently shown that administration of steroid containing extracts of the adrenal cortex produced thymus involution as well [3-5]. The availability of pure steroids finally confirmed that GC were the active substances of the adrenal cortex in this respect.
