Abstract Lymphocytic hypophysitis (LH) is a rare autoimmune disorder of the pituitary gland that presents with varying degrees of hypopituitarism due to pituitary infiltration and subsequent enlargement. The estimated prevalence is 1 in 7 to 9 million. Because of its nonspecific presentation and overlap with other sellar pathologies, diagnosis and management are often delayed. Herein we present a case of severe hyponatremia due to syndrome of inappropriate antidiuretic hormone secretion (SIADH) and secondary adrenal insufficiency from lymphocytic hypophysitis-induced panhypopituitarism in a post-partum female. A 43-year-old two weeks postpartum female presented with progressive headaches and peripheral vision disturbances. Brain MRI revealed a 2.3cm pituitary macroadenoma with mass effect on the optic chiasm and extension into bilateral cavernous sinuses. Visual field testing demonstrated bitemporal hemianopsia. Labs demonstrated panhypopituitarism, and she was started on appropriate hormone replacement therapy. At three weeks post-partum she underwent transnasal transsphenoidal debulking of the sellar lesion. One week post-operatively, she re-presented with progressive nausea, fatigue, and dizziness despite steroid repletion and no clear precipitating factor for adrenal crisis. Laboratory evaluation revealed severe hyponatremia with Na of 124mmol/L due to concomitant SIADH and secondary adrenal insufficiency. She ultimately required admission to the intensive care unit (ICU) for hypertonic saline due to concern for deteriorating vision and lack of response to fluid restriction. Pathology results from her transsphenoidal resection returned as lymphocytic hypophysitis. She was initiated on high dose glucocorticoids, prednisone 70mg daily, for management of both the lymphocytic hypophysitis and secondary adrenal insufficiency, resulting in correction of sodium levels and clinical improvement. Despite several attempts, she has been unable to wean off steroids due to worsening visual symptoms and is beginning rituximab. This case emphasizes the importance of considering an autoimmune hypophysitis as a rare, but reversible cause of hyponatremia in critically ill patients, particularly in post-partum females. While SIADH is a common cause of hyponatremia, its occurrence secondary to pituitary inflammation is exceptionally rare. Early recognition of this association is crucial as treatment can differ substantially from other causes of SIADH. It often requires corticosteroid therapy and hormonal replacement rather than fluid restriction alone. This case demonstrates the interesting pathophysiology of LH as a rare autoimmune pituitary disorder, and links endocrinologic disorders and critical care medicine in the multidisciplinary management of SIADH and adrenal insufficiency. This abstract is funded by: None
Ward et al. (Fri,) studied this question.