MON-038 Hormonal imbalance in encephalitis with increased intracranial pressure: a case report.

Abstract Disclosure: R.G. Vaca: None. A.N. Delgado Nieves: None. D. Slack: None. Case presentation A middle-aged Afro-American man with atrial fibrillation, scleromyxedema, euthyroid Hashimoto’s disease presented to the ER with progressive nausea, vomiting, and abdominal pain. Vital signs were normal. In the ER he developed dysarthria and altered mental status. CT head was normal, but MRI brain showed a ring-enhancing lesion in the dorsal medulla. Lumbar puncture was negative. His mental status declined, and he became comatose, developing respiratory failure and shock. An interval MRI showed new obstructive hydrocephalus with rhombencephalitis. Work up included a mid-day cortisol (5.2 ug/dL [2-14]) with an inappropriate response to ACTH stimulation test (13.5 ug/dL at 30 minutes, and 13.7 ug/dL at 60 minutes), concerning for adrenal insufficiency. Chemistry showed hypernatremia but normal potassium. TSH level was low (0.141 uIU/mL [0.4-4.2]), with undetectable total T3 (<30 ng/dL [nr, 40-193]) and free T4 (<0.42 ng/dL [0.8-1.5]). Low FSH 0.2 mIU/mL [1.3-19.3] and low-normal LH 1.86 mIU/mL [1.2-8.6] were also noted. Due to concern for pituitary dysfunction in the setting of hydrocephalus, stress dose hydrocortisone was started along with weight-based levothyroxine. Over the next days, the patient was weaned off vasopressors and tolerated a rapid corticoid tapering. 3 days after initial hormonal testing, reverse t3 resulted as elevated (44.6 ng/dL [9.2-24.1]). Discussion Hypopituitarism (HP) must be considered when there’s clinical suspicion of one or more hormonal deficiencies. Adrenal insufficiency, hypogonadism, and increased intracranial pressure, which has been shown to affect pituitary hormone secretion, raised concern for HP. Although a diagnosis of nonthyroidal illness (NTI) was later made, this case underscores the importance of early suspicion for HP and its severe complications, adrenal crisis (AC) and myxedema coma (MC), in critically ill patients. AC diagnosis mostly relies on chemistry findings and concomitant refractory shock. ACTH levels must be obtained to provide diagnostic guidance. MC also lacks specific or objective diagnostic criteria. Although rare, it should be considered due to its high mortality rate. Differentiating MC from NTI can be challenging in critically ill patients with central hypothyroidism as both entities present similarly. A 2014 MC scoring tool can be used but it excludes patients with suppressed TSH levels. Reverse T3 levels can be a useful marker in this scenario; however, it may take several days to result. ATA guidelines suggest treating MC with levothyroxine and advise caution about triiodothyronine (T3) in patients with cardiovascular disease. For NTI, the only option is T3; however, there’s lack of evidence to support treatment. In our patient a course of levothyroxine was started to treat a potential severe thyroid hormone deficit but T3 was avoided due to history of arrhythmia and uncertainty in MC diagnosis. Presentation: Monday, July 14, 2025