PMON39 A Perfect Storm – Multiple Causes of Hyponatremia in Patient With Pituitary Macroadenoma

INTRODUCTION: Adrenal insufficiency is a life threatening condition, and prompt diagnosis and treatment are necessary. Here we present a case of hyponatremia which was thought to be multifactorial due to secondary adrenal insufficiency in the setting of a pituitary macro-adenoma, central hypothyroidism, SIADH in the setting of nausea as well as analgesic use. CASE PRESENTATION: A 23 y.o female patient presented to the hospital with headaches. MRI of the head revealed a 2.2 cm pituitary mass abutting the optic chiasm with no edema and no need for urgent neurosurgical intervention. Outpatient endocrine workup demonstrated following labs: Na 135 mmol/l (ref range 135 - 145), afternoon cortisol 9.3 mcg/dl (ref range 5.0 - 23.0), ACTH 19 pg/ml (ref range 7.2-63), GH 3.8 ng/ml (ref range <=7.1), Prolactin 16.0 ng/ml (ref range 4.8 - 23.3). Due to persistent headaches, she was taking high doses of Naproxen, which resulted in nausea and vomiting, and led to another ED visit. At this time, she was found to have Na 117 mmol/l, Serum osmolality 246 mOsm/kg (re range 285–295), Urine osmolality 554 mOsm/kg (ref range 40 - 1,400), Urine Na 146 mmol/L. TSH was 0.16 mIU/ml (ref range 0.27 - 4.20) and free T4 was 0.49 ng/dl (ref range 0.80 - 1.90). Endocrine was consulted and the pathogenesis for hyponatremia was thought to be multifactorial including central adrenal insufficiency masked by central hypothyroidism. Her cortisol levels as detailed above were done early afternoon and could not exclude at least some degree of central adrenal insufficiency. Additionally, hypothyroid state can significantly decrease metabolism of cortisol thus preventing acute drop in cortisol levels. She also seemed to have concomitant syndrome of inappropriate antidiuretic hormone secretion (SIADH), driven by both the pituitary tumor as well as nausea and vomiting. On top of that for her severe progressive headaches she was treated with non-steroidal anti-inflammatory agents and tramadol, both known to associate with hyponatremia. She was started on intravenous hydrocortisone, and subsequently oral levothyroxine. She had improvement in her sodium levels and did not require Tolvaptan. She was discharged on hydrocortisone and levothyroxine with outpatient endocrine and neurosurgery follow up. She is currently awaiting neurosurgical intervention. DISCUSSION: Secondary adrenal insufficiency is more common than primary adrenal insufficiency. Establishing the diagnosis of secondary adrenal insufficiency is challenging as it is not typically associated with classical signs and symptoms of adrenal insufficiency. Clinical manifestations tend to be more indolent as they result from glucocorticoid deficiency only and there is preservation of the aldosterone and adrenal androgen axis. What makes our patient interesting is the several factors as mentioned above which contributed to her severe hyponatremia. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.