In patients with primary adrenal insufficiency, somatostatin administration resulted in more effective ACTH suppression in patients left on low cortisol than on cortisol replacement (18); in patients with Nelson's syndrome, octreotide was more efficient to lower ACTH, especially after temporary withdrawal of cortisol replacement, than in patients with Cushing's disease and high cortisol levels (19); and exposure to dexamethasone decreases the in vitro expression of SST2-mRNA in pituitary adenoma cells (20). This evidence concerns the gene POMC and primary adrenal insufficiency.