Thus, very little is known about the epidemiological, clinical, and molecular features of ACTH secreting NENs, and there is, to our knowledge, only one study published about predictive and prognostic markers of ECS in patients with NENs, indicating that severe hypercortisolism, hypokalemia, diabetes mellitus, and distant metastases were negative predictive factors [35]. This evidence concerns the gene POMC and Hypokalemia.