MON-136 BIUXX

Abstract Disclosure: R. Sharma: None. A Rare Case of Posterior Pituitary AdenomaRhea Sharma, MD, Ismat Shafiq, MD, G. Edward Vates, MD, PhD, Mahlon D. Johnson, MD, PhD. Objective: Pituitary tumors are rare, accounting for 10-15% of primary brain tumors, with the majority (99%) being anterior pituitary tumors (APT). This study presents a rare case of posterior pituitary tumor (PPT) in a healthy 34-year-old female. Methods: We reviewed the patient's medical history from EPIC electronic records and conducted a literature review on PPTs. Case: A 34-year-old healthy female presented with fatigue, exercise intolerance, and cognitive changes. She was referred to multiple specialists for chronic kidney disease (stage II) of unclear etiology, palpitations, and cognitive issues. An MRI of the brain revealed a 1.5 cm x 1.2 cm pituitary tumor, leading to referral to Pituitary Clinic. She reported a 60lb weight gain, headaches with nausea, vomiting, photophobia, constipation, hirsutism, breast enlargement with purple striae, and heat/cold intolerance.Given these findings, endocrinology work up was obtained which noted mildly elevated prolactin level of 93 ng/ml (normal: 4.8-23.3 ng/ml), AM cortisol at 24.3 ug/dl (normal 6-18.4 ug/dl), IGF 183 ng/ml (normal 78-274 ng/ml), TSH 1.58 uIU/ml (normal 0.27- 4.2 uIU/ml), free T4 1.1 ng/dl (normal 0.9-1.7 ng/dl). The salivary cortisol and 24-hour urine cortisol were both in the normal range. Given these findings, the tumor was diagnosed as a non-functioning pituitary tumor with possible stalk effect and asymptomatic prolactinoma. She underwent successful transsphenoidal resection due to the tumor's size and prolactinoma. Pathology identified the tumor as a granular cell tumor with thyroid transcription factor I (TTF-1) immunopositivity. Discussion: This case highlights a rare PPT presentation in a young woman with cognitive changes, exercise intolerance, weight gain, and unexplained CKD. After 5 years, she remains in full remission with improved symptoms and kidney function. PPTs are difficult to distinguish from anterior pituitary tumors based on initial clinical and imaging findings. Recent studies suggest that PPTs may have higher recurrence rates post-surgery than non-functioning APTs. Postoperative surveillance is challenging due to the lack of specific tumor markers. MRI remains the primary tool for detecting recurrence, but there is no consensus on optimal surveillance frequency. Some studies recommend annual MRIs for the first five years, transitioning to biannual imaging thereafter. In this case, annual MRIs were performed for the first two years, followed by biannual monitoring. This report adds to the limited literature on PPTs, particularly regarding management and surveillance in otherwise healthy patients. Presentation: Monday, July 14, 2025