MON-108 Granulomatous Hypophysitis due to Neurosarcoidosis Mimicking Pituitary Macroadenoma; a Rare but Important Differential Diagnosis

Abstract Disclosure: G. Hehar: None. A. Aluri: None. J. Jun: None. W. Jodeh: None. Background: Hypothalamic-pituitary sarcoidosis is an uncommon condition, occurring in 0.5-2.5% of patients with this granulomatous disorder and accounting for 1% of sellar masses. Although neurosarcoidosis is typically seen in a multisystem context, cases of pituitary involvement without typical features of sarcoidosis have rarely been described. The diagnosis is challenging due to non-specific features and further need for histologic confirmation. Clinical case: A 44-year-old female with history of hypertension and chronic sinusitis developed progressively worsening headache, dizziness and blurry-double vision for 3 months. CT scan of the head revealed a prominent pituitary gland measuring 1.6 x 1.2 x 1.6 cm and opacification of the paranasal sinuses. MRI of the pituitary revealed a T1 isointense, T2 hypointense homogenous mass in the sella and suprasellar cistern, with avid homogeneous enhancement postcontrast, measuring 1.7 x 1.2 x 1.5 cm, with displacement of the right internal carotid artery flow-void and compression of the optic chiasm. MRI also showed pansinus mucosal thickening. Laboratory evaluation of the hypothalamic pituitary axis was consistent with central hypothyroidism with low TSH of 0.041 uIU/mL (0.450-4.5 uIU/mL) and low free T4 of 0.68 ng/dL (0.82-1.77 ng/dL). Prolactin was slightly elevated at 50.8 ng/mL (4.8-33.4 ng/mL) and IGF1 was 42 ng/mL (49-240 ng/mL). Morning serum cortisol was not obtained prior to surgery. The patient underwent endoscopic transnasal transsphenoidal hypophysectomy and sinus surgery. Pathology revealed granulomatous inflammation involving the pituitary and sinonasal mucosa. CT of the chest was normal. Lumbar puncture showed normal opening pressure and mildly elevated total protein of 75 mg/dL consistent with inflammation. IgG levels and ANCA were normal. The patient was diagnosed with granulomatous hypophysitis due to neurosarcoidosis. She was started on high dose glucocorticoid treatment and thyroid hormone replacement. Conclusion: This case highlights a rare cause of apparent pituitary mass with hypopituitarism. Although uncommon, it is important to consider hypothalamic-pituitary neurosarcoidosis in the differential diagnosis of any pituitary lesion, even in the absence of typical features of sarcoidosis. Hypopituitarism in this setting is usually permanent. The treatment involves high dose glucocorticoids as first line therapy and immunosuppressive agents as second line. This entity can mimic pituitary macroadenoma and requires high index of suspicion to accurately diagnose and treat. A better understanding of features that may be specific to this disease could help clinicians in this challenging diagnosis. Presentation: Monday, July 14, 2025