Autonomous (unregulated) hormone production from a functioning pituitary adenoma (PA, non-cancerous pituitary tumor) can perturb this delicate equilibrium, manifesting a variety of clinical syndromes including ACTH-dependent Cushing’s syndrome (excess ACTH), acromegaly (excess GH), hyperprolactinaemia (excess prolactin), and hyperthyroidism (excess TSH). This evidence concerns the gene POMC and hyperprolactinemia.