Severe hyperprolactinemia associated with internal carotid artery aneurysm: differential diagnosis between prolactinoma and hypothalamic-pituitary disconnection.

Sellar and parasellar masses blocking inhibitory hypothalamic dopaminergic tonus can produce hyperprolactinemia. One of these conditions, seldom reported, is internal carotid artery aneurysm causing pituitary stalk compression and hyperprolactinemia, the majority of which is related to small increases in serum prolactin levels. The aim of this study is to report the case of a patient with an internal carotid aneurysm and severe hiperprolactinemia. A 72 years old female patient, on oncology follow-up for clinically controlled cervical carcinoma, was evaluated due to worsening chronic headaches. During the investigation, computed tomography and magnetic resonance imaging (MRI) showed a sellar mass associated with high prolactin level (1.403 microg/L) that initially was considered a macroprolactinoma, and treated with bromocriptine. However, subsequent pituitary MRI suggested an internal carotid aneurysm, which was confirmed by an angioresonance imaging of cerebral vessels. On low bromocriptine dose (1.25 mg/day), there was a prompt normalization of prolactin levels with a great increase (> 600 microg/L) after withdrawal, which was confirmed several times, suggesting HPD. We report a patient with internal carotid artery aneurysm with severe hyperprolactinemia never reported before in patients with HPD, and the need for a differential diagnosis with macroprolactinomas even considering high prolactin levels.