We describe a unique case of severe ACTH-dependent Cushing's syndrome due to ectopic corticotropin production by medullary thyroid carcinoma in a male patient of 39 years old with calcitonin level more than 4000 pg/ml (&lt;11,8), thyroid nodule, multiple neck jugular and central lymphnodes. This evidence concerns the gene POMC and medullary thyroid gland carcinoma.