Growth factors and pericellular components as a local signalling relay in the action of systemic hormones

Recent years have shown that peptidic signals, originally identified as growth factors, may represent a local signalling system involved in the regulation of cell function under the dependence of systemic hormones. As an example, (i) adrenocortical cells are highly sensitive to transforming growth factor-beta (TGF beta) which is a powerful inhibitor of their differentiated functions; (ii) adrenocortical cells produce and secrete TGF beta, which is present in the adrenal cortex in situ; (iii) adrenocorticotropin (ACTH), which is the best known positive effector of adrenocortical functions induces an up-regulation of TGF beta receptors in adrenocortical cells. Altogether, these observations suggest that TGF beta may be a local signalling system acting in balance with the systemic hormone ACTH to eventually tune the ability of adrenocortical cells to produce corticosteroids.