Another special consideration in patients with ZES is the increased incidence of Cushing syndrome that has been described in these patients, which is due to a corticotroph pituitary adenoma causing Cushing disease, as opposed to ectopic ACTH secretion from an islet cell tumor which is more commonly seen in conjunction with sporadic gastrinomas (110). The gene discussed is POMC; the disease is gastrin-producing neuroendocrine tumor.