Abstract Disclosure: U. Siddiqui: None. M. Ahmad: None. K. Abiko: None. P. Ucciferro: None. Pituitary apoplexy is characterized by hemorrhage or infarction of the pituitary gland occurring after growth of a pre-existing adenoma. These adenomas are often asymptomatic, however, hemorrhage can compress surrounding cranial nerves and cause symptoms. We report a case of a 48-year-old male who presented with headache and third nerve palsy, found to have pituitary apoplexy despite negative initial CT imaging. Hospital Course: A 48-year-old man with a past medical history of asthma, cirrhosis, type 2 diabetes mellitus, hypertension and end stage renal disease presented to the emergency room for bitemporal headache. The headache was associated with right-sided blurry vision and ptosis. He was hypertensive to 166/79 mmHg, bradycardic to 58 beats per minute, afebrile with a temperature of 36.8 C with a respiratory rate of 18 breaths per minute. He was noted to have ptosis and inferolateral deviation of his right eye. Initial labs demonstrated the following: sodium 139 mmol/L, potassium 5.2 mmol/L, creatinine 8.44 mg/dL (baseline 6.5 mg/dL), bicarbonate 20 mmol/L, and hemoglobin 8.2 g/dL (baseline of 8-9 g/dL). The patient’s CT head without contrast and CT angiogram head and neck which were negative for acute infarct or hemorrhage, however, the patient’s MRI demonstrated a 2.1 x 2.1 x 1.4 cm macroadenoma with suprasellar extension and mild elevation of the optic chiasm. Further testing demonstrated a normal thyroid stimulating hormone level of 0.74 uIU/ml (normal 0.3-5.0 uIU/ml), low normal free t4 of 0.7 ng/dL (0.7-1.7 ng/dL), ACTH of <9 pg/ml (normal 9-46 pg/ml), morning cortisol of 1.3 mcg/dL (normal of >18 mcd/dL), total testosterone <10 ng/dL (normal 270-1070 ng/dL), follicular stimulating hormone of 2.2 mIU/ml (normal 1.5-12.4 mIU/mL) and a prolactin of 49 ng/ml (normal 0-19 mg/ml). Due to the patient’s symptoms and imaging findings he underwent transsphenoidal resection of tumor. Prior to the procedure he was placed on stress dosed steroids with IV hydrocortisone. After the procedure, the patient was weaned off IV hydrocortisone and continued on oral 15 mg of hydrocortisone in the morning and 5 mg in the evening. A repeat free T4 after the procedure was 0.9 ng/dl and the patient was not discharged on levothyroxine supplementation. He follows up with endocrinology as an outpatient and has had resolution of his right sided ptosis and vision changes. Discussion: Pituitary apoplexy presents in a variety of different ways including headache, nausea, altered mental status, and hormonal dysfunction. Third nerve palsy is a potential presentation of this uncommon condition and should be considered even with negative initial CT imaging. Through our case we hope to highlight this manifestation of pituitary apoplexy as, if the etiology of third nerve palsy remains elusive, pituitary apoplexy should be considered as a differential and further imaging should be obtained. Presentation: Saturday, June 17, 2023