Development of a Macroprolactinoma in Association with Hormone Replacement Therapy in a Perimenopausal Woman with Presumed Idiopathic Hyperprolactinemia

Abstract

To describe a 48-year-old woman with presumed idiopathic hyperprolactinemia, who was found to have a macroprolactinoma after receiving hormone replacement therapy for almost 3 years. We present a detailed case report, including a chronologic summary of clinical and laboratory findings as well as the drug history of our patient. The related literature is also reviewed. Premenopausal women with idiopathic hyperprolactinemia or microprolactinomas (<1 cm) are treated with dopamine agonists if fertility is desired or galactorrhea is bothersome. Otherwise, estrogens and progestational agents may be prescribed to regularize menses and prevent osteoporosis. Several case reports of prolactinoma formation or enlargement after exposure to exogenous estrogens have been published. In our patient, a perimenopausal woman with presumably idiopathic long-standing hyperprolactinemia, a macroprolactinoma developed within 3 years after initiation of hormone replacement therapy for management of perimenopausal symptoms. The only clue for ordering a pituitary imaging study in this case was a substantial increase in the level of the serum prolactin. Treatment with cabergoline normalized the patient's serum prolactin level and considerably decreased the size of her pituitary adenoma. It is postulated that exogenous estrogens could have an important role in tumor development or growth in some patients with idiopathic hyperprolactinemia. Therefore, it is recommended that women with idiopathic hyperprolactinemia or microprolactinomas treated with estrogens be considered for concomitant therapy with dopamine agonists. In all cases, serum prolactin levels should be diligently monitored.