FRI318 A Case Of Mixed Growth Hormone And Prolactin-secreting Giant Pituitary Macroadenoma

Disclosure: A. Khan: None. I. Alpertunga: None. V. Kantorovich: None. Introduction Co-secretion of prolactin (PRL) and growth hormone (GH) from a single pituitary adenoma is an established entity in the medical literature and present in about 5% of the cases. Guidelines recommend to obtain an insulin-like growth factor-1 (IGF-1) in patients with prolactinoma at the time of initial diagnosis. Our case describes the management of a giant pituitary macroadenoma co-secreting PRL and GH. Case A 20-year-old male with history significant for schizophrenia presented with visual disturbances and discharge from his left nipple. His prolactin level (PRL) was noted to be elevated at 12,396 (4.0-15.2) ng/ml on work-up during recent prior investigation. On physical exam, he had bilateral temporal visual field deficit as well as dysfunction in upward gaze of left eye. Head imaging showed a 7.5 x 6.2 x 5 cm associated with remodeling of the sella turcica and expanding into the suprasellar space and significant mass-effect on the adjacent frontal lobes bilaterally, mild mass-effect on the adjacent optic chiasm with significant surrounding vasogenic edema and compressing the bilateral anterior cerebral arteries. Patient was started on low dose cabergoline in caution of prevention of possibility of rapid response-related significant volume contraction of the tumor with possibility of reactive edema. The dose of cabergoline was rapidly titrated up to 3 mg bi-weekly with minimal prolactin fluctuation of PRL between 12,000 and 16,000 ng/ml. Because of mild atypical acromegalic facial features, patient had GH axis assessment. IGF-1 level came back elevated at 529 (83-456) ng/ml with a high IGF Binding Protein- 3 of 8.9 (2.9-7.2) mg/l. He was started on octreotide titrated up to a dose of 150 mcg three times daily. Repeat MRI brain did not show tumor shrinkage. Subsequently, patient underwent bifrontal craniotomy for resection/debulking of parasellar tumor. PRL dropped to 931 ng/ml immediately after surgery. At the time of writing, pathology of the tumor and repeat IGF-1 level is pending. Patient was monitored closely in the ICU with a steroid taper postoperatively. Discussion Dopamine agonists are the first-line therapy for medical treatment of hyperprolactinemia but can also suppress GH and IGF-1 levels. However, in acromegaly, cabergoline is utilized mostly for small adenomas with mild elevation of IGF-1. In our case, we decided to use a combination of cabergoline and somatostatin receptor analog, octreotide. However, given the giant adenoma with very high PRL and IGF-1 levels, patient showed a poor response to medical therapy, and given the impending threat to patient’s vision, he underwent surgical debulking. Our case highlights the management of a giant, mixed hormone-secreting pituitary adenoma. Presentation: Friday, June 16, 2023