Incubation of primary cultures from corticotroph adenomas with cortisol causes a reduction in ACTH levels, indicating some response to negative feedback15; however, dexamethasone treatment causes less inhibition of ACTH release and POMC mRNA levels in cultured corticotroph adenoma cells than non-adenomatous pituitary cells16. The gene discussed is POMC; the disease is ACTH-producing pituitary gland adenoma.