Giant Prolactinoma: Challenges in Management

Prolactinomas are the most common form of pituitary adenomas, 90% of which are microprolactinomas measuring <1 cm. A giant prolactinoma is defined as a prolactinoma measuring >4 cm with a serum prolactin level of >1000 ng/mL. We report a case of giant prolactinoma causing optic nerve compression that initially responded well to cabergoline and later developed intratumoral hemorrhage requiring transsphenoidal resection.

A 47-year-old man presented with blurry vision and intermittent headaches for 6 months. Visual field (VF) testing demonstrated bitemporal VF defect, which prompted magnetic resonance imaging of brain that showed a 4.1 × 3.1 × 3.1-cm pituitary macroadenoma with suprasellar extension compressing the optic chiasm. Laboratory evaluation revealed an increased prolactin level, low testosterone level, inappropriately normal luteinizing hormone level, and follicle-stimulating hormone level consistent with central hypogonadism. Cabergoline 0.5 mg twice weekly was started. Repeat VF testing and prolactin level in 4 weeks after starting cabergoline showed improvement. Nine months later, his symptoms worsened, and repeat magnetic resonance imaging showed intratumoral hemorrhage and that the size of the tumor had increased. He underwent an emergent transsphenoidal resection. After surgery, he developed central adrenal insufficiency and central hypothyroidism requiring steroid and thyroid hormone replacement.

Only a few cases of giant prolactinomas have been reported, and no clear guidelines for management of giant prolactinomas have been established. First-line medical management includes dopamine agonists such as cabergoline and bromocriptine.

The dilemma between medical management and surgical management occurs during initial presentation of giant prolactinoma with VF defect. Our case report highlights the challenges and complications encountered in the treatment of a patient with giant prolactinoma.