Abstract Disclosure: N. Akabogu: None. S. Dejhansathit: None. F. Marium: None. B. Stanley: None. E.M. Bazuaye: None. L.S. Krusniak: None. L.G. Kurukulasuriya: None. U.Z. Khan: None. Background: Sheehan syndrome, which is also known as postpartum pituitary infarction, refers to the necrosis of the anterior pituitary gland due to postpartum hypovolemia, hemorrhage, shock, resulting in various degrees of hypopituitarism. The pituitary gland enlarges during pregnancy due to estrogen stimulation and becomes hyper-vascular, making it prone to infarction with postpartum hemorrhage. The initial symptoms include hyponatremia, weakness, weight loss, but the most prominent specific symptoms are inability to nurse and postpartum amenorrhea. Depending on the severity of hypopituitarism, symptoms may develop within the first few days to weeks after delivery or may take months to years to develop. Case presentation: 35year-old Caucasian female with a medical history of gestational diabetes, hyperlipidemia, and hypertension, who presented to the hospital with flu-like symptoms, leg pain, abdominal pain, and proximal muscle weakness. The evaluating hospitalist observed that patient appeared sluggish and spoke with a deep coarse voice, which concerned him for hypothyroidism. Thyroid function test revealed undetectable free T4 with inappropriately normal TSH of 1.38 – consistent with secondary hypothyroidism. Additional history from patient uncovered 9 months history of constant fatigue, weight gain, dry skin, hair loss, cold intolerance, and intermittent ankle swelling. There is no history of brain irradiation or head trauma. She has 4 biological children, and her last childbirth 3years ago was complicated by severe bleeding from her incision site, requiring transfusion of 6 units of blood. She has been amenorrheic since and is neither on birth control nor had hysterectomy. Physical exam showed mildly enlarged tongue, diffuse pallor, dry scaly skin on upper arms, scanty eyebrows, and slowed speech. Further work-up for pituitary insufficiency showed secondary adrenal insufficiency, secondary hypogonadism, low prolactin, and growth hormone deficiency. There was no evidence of AVP deficiency. Other lab and clinical findings were hypoglycemia, hyperlipidemia, elevated CK, elevated Cr, pericardial effusion, and diastolic hypertension. Pituitary MRI showed markedly attenuated and flattened pituitary gland with no focal mass. Patient was given stress dose hydrocortisone and thyroid hormone replacement, initially IV then oral. Following hydrocortisone and thyroid hormone replacement, her diastolic BP, hypoglycemia, CK, and Cr improved. Further management plans include initiating estrogen (plus progesterone) for bone health. Conclusion: Although Sheehan syndrome is rare in developed countries, it does occur. This case emphasizes the importance of detailed history taking, to discover the root of patients’ presentation. Even though TSH is the screening test for thyroid disease, when pituitary etiology is suspected, it is important to also check a free T4. Presentation: 6/1/2024