Syndrome de Cushing induit par le GIP : expression clinique d'un récepteur ectopique

Abstract

The pathophysiology of non-ACTH-dependent adrenal nodular hyperplasia and tumors resulting in Cushing's syndrome is still largely unknown. Previous in vitro studies have demonstrated the presence of ectopic (mostly G-protein-coupled) receptors in such tumors, suggesting that they may not be functionally autonomous. Recently, two groups, including our own, studied three patients with Cushing's syndrome of adrenal origin in whom cortisol production was food-dependent. In two such patients presenting macronodular adrenal hyperplasia, in vivo and in vitro studies demonstrated that the syndrome was secondary to an aberrant adrenal responsiveness to the normal postprandial fluctuations of GIP (gastric inhibitory polypeptide) levels. These patients constitute a clinical expression of the ectopic presence of GIP receptor in adrenocortical cells. It remains to be determined what are the frequency, diversity, molecular mechanisms, and pathophysiological role Of the ectopic expression of membrane receptors in tumors originating from endocrine cells or from cells modulated by hormones.