Reported cases highlight the diagnostic challenges and aggressive nature of MTC-induced ectopic ACTH secretion, often presenting with severe hypercortisolism and advanced disease at diagnosis, although this is highly unusual.8, 9, 10, 11 The connection between these 2 conditions highlights the importance of considering MTC as a potential cause of ectopic ACTH production in patients with CS. This evidence concerns the gene POMC and medullary thyroid gland carcinoma.