We report on 2 cases of hyperprolactinemia associated with thyroid dysfunction. The changes in clinical symptoms and serum prolactin levels highly corresponded to thyroxine therapy. The first case had galactorrhea associated with overt hypothyroidism and pituitary microadenoma. All abnormalities disappeared after thyroxine therapy. The second case had galactorrhea resistant to dopamine agonist therapy and demonstrated improvement after thyroxine replacement. Hyperprolactinemia recurred after withdrawal of the dopamine agonist. We review the literature on hypothyroidism-related hyperprolactinemia and discuss the current opinions about this condition.