SUN-433 Pituitary Dysfunction Secondary to a Large Cavernous Internal Carotid Artery Aneurysm

Abstract

Background: Intracranial aneurysms extending into the sellar space and leading to pituitary dysfunction are exceedingly rare. This type of vascular lesions may be responsible for less than 0.2% of cases of hypopituitarism. Herein, we present a case of hypopituitarism and hyperprolactinemia secondary to a large unruptured left cavernous internal carotid artery aneurysm with intra- and suprasellar extension. Clinical case: An 81-year-old woman with past medical history of long-standing primary hypothyroidism was noted to have a suppressed serum TSH (0.007 uU/mL [0.400 - 5.500]) on routine laboratory studies. Prior to this, she had been on a stable dose of levothyroxine replacement for several years and her TSH level had been maintained within the normal reference range. Subsequent laboratory studies showed an elevated prolactin level (173.4 ng/mL [4.5 - 26.8]), inappropriately low gonadotropin levels for a post-menopausal woman (FSH 4.4 mU/mL [20 - 100]; LH 0.8 mU/mL [>20]), normal IGF-1 (96 ng/mL [27 - 170]), and a low morning cortisol level (2.5 ug/dL (5.3 - 22.5)] with an inappropriately normal ACTH level (12 pg/mL [<47]). Her 60-minute cortisol level was <20 ug/dL during an ACTH stimulation test. The patient was started on steroid replacement and was continued on levothyroxine. A brain MRI was performed and demonstrated an area of heterogeneous unenhanced T1-weighted signal intensity and T2 signal void in the sellar space, measuring approximately 15 mm in diameter. The radiological differentials included a proteinaceous pituitary cyst or a vascular aneurysm. A brain MRA was then obtained for better characterization of the lesion, which revealed a large left cavernous internal carotid artery aneurysm (13 x 17 x 16 mm), completely filling the sellar space and extending into the suprasellar region. The patient was referred to neurosurgery and underwent a successful pipeline embolization of the aneurysm. At two months follow-up, her TSH was 0.159 uU/mL and her prolactin level was 140.3 ng/mL. Conclusion: Aneurysms with intrasellar extension should always be considered in the differential diagnosis of sellar lesions. When compared with cases of nonfunctioning pituitary macroadenomas, intrasellar aneurysms may result in comparable dysfunction in pituitary hormone production and hyperprolactinemia. Endocrine abnormalities are usually irreversible and permanent hormone replacement therapy is necessary. Long-term follow-up may elucidate pituitary function recovery after effective aneurysm treatment.