Giant Invasive Prolactinoma Presenting with Unilateral Exophthalmos in a Patient with MEN1

ABSTRACT Objective: Management of an unusual case of a giant invasive prolactinoma in a patient with multiple endocrine neoplasia type 1 (MEN1). Methods: We present complete clinical presentation, imaging, and biochemical features from a unique case of a giant invasive prolactinoma. Results: We report an unusual case of a giant invasive prolactinoma in a 29-year-old man presenting with right eye exophthalmos, headache, and bitemporal vision loss. Magnetic resonance imaging revealed a large sellar mass with suprasellar extension and extension into the right orbit. An endocrine work-up revealed elevated serum prolactin (32,000 ng/mL). On screening, the patient had high serum calcium, low phosphorous, and high parathyroid hormone. A computed tomography scan from neck to pelvis showed an enlarged left inferior parathyroid gland and bilateral renal calculi. The patient was genetically confirmed to have a MEN1 mutation. The patient was treated with the long-acting dopamine agonist, cabergoline, with escalating doses under supervision. Within 1 week, prolactin levels reduced to 3,300 ng/mL. Over a period of 1 year, with 2 mg/week of cabergoline, serum prolactin levels dropped to 55.85 ng/mL, with a significant reduction of tumor mass and exophthalmos. Conclusion: To the best of our knowledge, no previous patients with MEN1 and a giant invasive prolactinoma with orbital extension have been reported. We highlight the successful use of a dopamine agonist in the treatment of giant invasive prolactinoma with exophthalmos in the MEN1 setting. Abbreviations: MEN1 = multiple endocrine neoplasia type 1 MRI = magnetic resonance imaging PRL = prolactin