Cytokines: autocrine and paracrine roles in the anterior pituitary.

In addition to their role as lymphocyte messengers, cytokines also act at the anterior pituitary gland as autocrine or paracrine regulators of anterior pituitary function. As a cellular and molecular basis for this latter role, receptors for interleukin (IL)-1, IL-2 and IL-6 have been demonstrated in the pituitary of several species, as the endogenous production of the homologous cytokines. Additional cytokines are synthesized in or alter the function of the pituitary. IL-1, IL-2 and IL-6 regulate not only the secretion of pituitary hormones, but also the growth and proliferation of pituitary cells. This latter action suggests that intrinsically produced cytokines play a role in the pathogenesis of pituitary adenomas. Cytokines thus constitute a complex autocrine or paracrine network that contributes to the regulation of anterior pituitary physiology and pathophysiology.