Endocrine Abstracts

Giant prolactinomas are rare pituitary tumors, defined as adenomas greater than 4 cm, with extrasellar extension, presenting with PRL levels > 1000 ng/dl. Dopamine agonists (DA) are the first-line treatment. Most (90%) of giant prolactinomas occur in men.

We describe two cases of giant prolactinoma. A 17 years man presented with frontal headache, gradual visual deficit, nausea and dizziness. MRI demonstrated a sellar tumor of 6.4 cm with extrasellar extension, compressing the right optic nerve and optic chiasm. Laboratory testing revealed an elevated PRL (19093 ng/ml), hypogonadotropic hypogonadism, secondary hypothyroidism and adrenal insufficiency. Perimetry detected right side temporal quadrantanopsia and left side temporal hemianopsia. Treatment with cabergoline 2 mg/week resulted in PRL decrease by 88% after two months, later up-titrated to 4.5 mg/week during the follow-up. Most recent CT scan, after five years of cabergoline, revealed marked reduction in tumor size to less than 4 cm and PRL normalization (13.78 ng/ml) but persistent central hypothyroidism.

The second patient, a 27 year-old man, presented for headache, recurrent posterior epistaxis and decreased libido in the last 6 months. CT scan showed an intra- and perisellar extensive tumor measuring 6.0 cm. Laboratory evaluations showed PRL levels of 31398 ng/ml and central hypogonadism. The other pituitary tests and visual field examination were normal. Cabergoline 2 mg/week was started, resulting in 80% reduction of PRL in the first 48 hours.

Despite the similar size and PRL values, giant prolactinomas in men can have a heterogeneous profile at diagnosis, from the classical visual field deficiency and pituitary failure to normal visual field and almost normal pituitary function. Correct diagnosis is capital to ensuring appropriate treatment. Lifelong follow-up is usually needed.