Abstract Disclosure: I. Dosunmu: None. A. Alvi: None. S. Kaufman: None. A. Malik: None. Introduction: Sheehan syndrome is defined as ischemic necrosis of pituitary gland following massive postpartum hemorrhage. The majority of cases remain undiagnosed for many years after delivery. We present a unique case of late onset of Sheehan syndrome 23 years after the last childbirth which was complicated by hemorrhage. Although the syndrome can present with panhypopituitarism, most patients have partial hormone deficiency which leads to a delay in the diagnosis. Patients can remain asymptomatic for many years until the body is exposed to stressful situations. This is what we believe caused our patient to develop hyponatremia after staying symptom free for 23 years. Case Description: A 46-year-old female with no medical history presented with abdominal pain and dark colored urine. Her initial vital signs were normal. Labs showed sodium of 132 mmol/L, AST of 552 U/L, ALT of 518 U/L, ALP of 196 U/L, GGT of 166 U/L. CT scan of abdomen, liver ultrasound, and liver biopsy were unremarkable. AMA was positive with value of 1.98, consistent with diagnosis of primary biliary cholangitis. On day 2 her blood pressure decreased to 76/42 mmHg and her sodium decreased to 129mmol/L and on day 5 her blood pressure was 88/43mmHg and her sodium decreased to 122mmol/L. TSH was found to be 2.54 uIu/ml. Upon further evaluation by endocrinology, patient appeared to have sluggish speech and appeared edematous particularly in her face. A free T4 was found to be less than 0.07 ng/dl and cortisol 0.5 mcg/dl, and ACTH 22.4 pg/ml, FSH of 4.2 mIU/ml, LH 1.3 mIU/ml. On further questioning, patient confirmed history of complicated childbirth 23 years ago requiring multiple transfusions and a hysterectomy and she reported agalactorrhea after delivery. Brain MRI confirmed empty sella and she was diagnosed with Sheehan syndrome. She was started on levothyroxine and hydrocortisone and ursodiol for PBC. Discussion: Delayed onset Sheehan's syndrome stems from inadequate blood supply or ischemia to the pituitary gland during childbirth. Diagnosis can be challenging due to its gradual onset and vague presenting symptoms. In our patient, the possibility of Sheehan syndrome was suspected after evaluation for hyponatremia revealed central hypothyroidism and secondary adrenal insufficiency. 
The immediate initiation of hydrocortisone followed by levothyroxine, resulted in the normalization of blood pressure and sodium and an increase in free T4 levels from <0.07 to 0.26 four days after hormone initiation. Early diagnosis and prompt treatment are crucial for the best outcomes. Our patient reported feeling much better and denied any symptoms 6 months after discharge. Conclusion: Delayed onset Sheehan's syndrome is a rare but important condition that can occur months or years after childbirth. Early diagnosis, proper medical management, and hormone replacement therapy are essential for improving the quality of life for affected women. Presentation: 6/2/2024