MON-137 Hemorrhage of Pituitary Microadenoma Leading To Isolated Secondary Adrenal Insufficiency

Abstract Disclosure: Y. Rapoport: None. J. Eapen: None. A. Chang: None. Isolated secondary adrenal insufficiency (AI) typically arises from chronic glucocorticoid use or widespread hypothalamic-pituitary axis dysfunction. This case highlights a rare presentation of isolated secondary AI caused by hemorrhage of a 5mm pituitary microadenoma and underscores the importance of a thorough evaluation, even in pituitary microadenomas. 53 year old female presented to the hospital for visual changes, headache and fatigue. The patient reported progressively worsening vision and headaches over 4-5 years, with a notable decline in vision four months prior to presentation. In the emergency department, patient was orthostatic by blood pressure and symptoms along with severe malaise. Pituitary MRI demonstrated a pituitary microadenoma with central hemorrhage measuring 5 × 5.5mm. Preoperative laboratory findings at 4am demonstrated:ACTH: 4.2 pg/mL (10-60 pg/mL)Cortisol: 8.3 µg/dL (10-20 µg/dL)TSH: 4.29 µIU/mL (0.27- 4.20 µIU/mL)Free T4: 1.26 ng/dL (0.93-1.70 ng/dL)Prolactin: 26.4 ng/mL (4.8-23.3 ng/mL)IGF-1: 94 ng/mL (53-234 ng/mL) She underwent transsphenoidal resection of the pituitary adenoma with pathology revealing necrotic cells of uncertain identity and proteinaceous material. Days 3 and 4 post-operative cortisol levels were 3.5µg/dL and 6.5µg/dL respectively and the patient was discharged on Hydrocortisone therapy. Outpatient follow up demonstrated multiple low morning cortisol levels, consistently below 5µg/dL and inappropriately low-normal ACTH values, ranging between 10-20pg/mL. While on the Hydrocortisone, the patient reported significant clinical improvement with her malaise and is doing well as of today. Pituitary adenomas are generally benign neoplasms, with primary clinical concerns being hormonal dysregulation due to unregulated secretion or mass effect. Pituitary pathology rarely causes isolated adrenal insufficiency, as it is more often associated with other hormonal deficiencies or panhypopituitarism involving multiple axes (e.g., TSH, LH, FSH, GH, prolactin). Reports of pituitary hemorrhage in microadenomas along with isolated secondary adrenal insufficiency is exceedingly rare. The relatively preserved levels of other pituitary hormones in this patient suggest selective damage to ACTH-secreting cells within the anterior pituitary, highlighting the heterogeneity of apoplexy presentations. Presentation: Monday, July 14, 2025