Introduction: Empty Sella syndrome (ESS) is characterized by subarachnoid space herniating into the Sella turcica, causing displacement or flattening of the pituitary gland. Primary ESS has an unknown etiology, secondary ESS may be caused by trauma, infection, adenoma, ischemia, surgery, pharmacological or radiological Rx. It has been noted in 5-23% of the population, usually found incidentally in autopsies or imaging. 25% to 50% of patients have endocrine abnormalities (panhypopituitarism, DI, DM type 2, irregular menses). Headache or ophthalmological symptoms may be seen. Case summary: 55-year-old AAF with Hx of anemia, presented with lethargy and acute encephalopathy after several months of progressively worsening dizziness, muscle weakness, and fatigue. For the past few days, her appetite was poor. She also complained of cold intolerance, brittle hair, dry skin, and occasional constipation. Denied headache, blurry vision, neck pain, palpitation, previous head imaging, trauma or surgery. Remote history included an uncomplicated pregnancy; menopause occurred several years ago. Found to be hypoglycemic with blood glucose 35 mg/dl. Six D50 ampules initially improved her hypoglycemia but blood glucose quickly dropped thereafter. Placed on D5 drip; with the same results. A&O to place and person only, lacked a goiter. Lab work revealed low morning serum cortisol <1.2 mcg/dl (10-20 mcg/dl),high TSH 37.1 mU/L (0.4-4.5Mu/L), low free T4 0.2 mcg/dl (4.5-11.2 mcg/dl), low insulin 1.6 mcU/ml (4-30 mcU/dl), low C peptide 0.48 ng/ml (1.1-22 ng/ml), elevated prolactin 31 ng/ml (2-29 ng/dl), and low FSH 10 mlU/ml (26-134 mlU/ml). ACTH stimulation test revealed adrenal insufficiency. Started on IV Dexamethasone 2mg BID, hypoglycemia resolved (later weaned to prednisone 5mg BID). In view of hypothyroidism, adrenal insufficiency, and low FSH in post-menopause, hypopituitarism was suspected. MRI brain revealed empty sella without micro- or macroadenoma. Discussion & Conclusion: PES is usually asymptomatic but can present with endocrine, neurologic, or visual symptoms. A fraction of patients present with nonspecific headache, dizziness, or cranial nerve disorders. Others may have ophthalmological symptoms such as blurry or decreased vision, or mild papilledema. Though mild hyperprolactinemia and various levels of hypopituitarism have been noted, it is rare that adult patients are hospitalized for undiagnosed hypopituitarism with refractory hypoglycemia or severe hyponatremia. Panhypopituitarism is noted in only 2% of ESS patients. Our case represents a rare clinical presentation of primary ESS, with no known trauma, surgery, or ischemia. As clinicians, we should include ESS in our differential when assessing patients presenting with hypopituitarism, refractory hypoglycemia, or neurological/visual symptoms. MRI brain should be obtained if ESS is suspected. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.