Aberrant expression of GIP (Gastric Inhibitory Polypeptide) receptor in anadrenal cortical adenoma responsible for a case of food-dependent Cushing's syndrome

A 33 year old,woman was investigated for an atypical case of Cushing's synd rome with suppressed early morning plasma cortisols. Chronic hypercortisoli sm was confirmed by classical biological criteria (24h urinary cortisol exc retion, dexamethasone suppression tests); more detailed dynamic and pharmac ological tests revealed unanticipated features spontaneous circadian plasma cortisol variations showed post prandial peaks; they could be induced by o ral - but not intraveinous - glucose tolerance tests and were inhibited by the concomitant administration of Sandostatin (a somatostatin analog). Adre nal CT scan identified a 2 cm unilateral adenoma with ipsilateral and contr o lateral atrophy Surgical removal of the tumor cured the hypercortisolism with hypocortisolism. Comparative analysis of the tumoral and normal tissue s showed that only the former responded in vitro to GIP (Gastric Inhibitory Polypeptide) and contained the specific mRNA of the GIP receptor. This cas e illustrates a nets pathotophysiological mechanism of tumorigenesis due to the aberrant expression of a seven transmembrane domain receptor in a tumo ral tissue. The nature of the given receptor induced a particular clinical phenotype related to food intake.