FRI482 Severe Hypothyroidism: A Lack Of Standardized Care For Patients At Risk Of Myxedema Coma

Disclosure: S. Abdurrahman: None. P. Thakkar: None. E. Kasiri: None. L. Belalcazar: None. Introduction: Myxedema coma (MC) is a rare complication of severe hypothyroidism (HT). MC is diagnosed clinically and often precipitated by a major acute event. While most physicians support rapid and aggressive management of MC to reduce mortality, there is no consensus on how to approach patients with severe HT at risk of MC. We present two cases that illustrate this treatment gap. Case Presentation: CASE 1: A 76-year-old woman with 9 years of primary HT presented to the hospital after a recent fall; she was found to have an intertrochanteric fracture. The patient reported fatigue, anorexia, and inability to perform activities of daily living. On exam, she was malnourished and intermittently somnolent. Her pulse rate was 84/min; she had no hypothermia. Labs were significant for TSH of 195 mIU/L (0.45 - 4.70 mIU/L) and an undetectable Free T4 (FT4) at <0.07 ng/dL (0.78 - 2.20 ng/dL). She was started on her prescribed home dose of levothyroxine (LT4) of 100 mcg PO daily (1.9 mcg/kg Ideal body weight [IBW]). Given the severe HT and risk of MC, surgery was deferred. More aggressive LT4 therapy begun the next day with 200 mcg orally and an additional dose of 100 mcg IV; concern for malabsorption was raised. On Day 3, she received 150 mcg IV of LT4 and her FT4 level was 0.75 ng/dL the following morning (average equivalent PO LT4 dose: 204 mcg/day, ∼2X replacement dose). She was given another dose of LT4 150 mcg IV and underwent surgical fixation the next day without complication. CASE 2: 27-year-old woman with 10 years of primary HT and non-adherence to LT4 therapy due to fear of palpitations. The patient presented to the hospital, after a recent miscarriage, with diarrhea due to clostridium difficile infection. On exam, she was alert and without hypothermia, but had a pericardial effusion. EKG was abnormal; labs showed hyponatremia, TSH of 147 mIU/L and an undetectable FT4 level. She refused LT4 on admission but agreed subsequently. An LT4 dose of 150 mcg IV daily was administered for 2 days with a follow-up FT4 level of 0.5 ng/dL (average equivalent PO LT4 dose: 187.5 mcg/day, ∼2.5 X replacement dose). Her LT4 dose was decreased to 100 mcg IV on Day 3. Given improvement of diarrhea, she was started on PO LT4 at a maintenance dose of 75 mcg daily (1.6 mcg/kg IBW per day) and discharged. Repeat labs 2 weeks later showed a TSH: of 5.52 mIU/L (0.45 - 4.70 mIU/L) and a free T4 of 1.17 ng/dl (0.78 - 2.20 ng/dL). Discussion: There remains a gap on how to systematically approach thyroid replacement in individuals with severe HT who present with an acute stressor and are at risk of MC. Our patients tolerated initial daily LT4 doses equivalent to 2-2.5 times their PO maintenance dose, with improvement in clinical status and circulating hormone levels. Our cases suggest that 3-4 days of LT4 approximating 2 times maintenance dose may expedite recovery of euthyroidism and reduce the risk of MC in these high-risk patients. Further studies are needed to inform practice. Presentation: Friday, June 16, 2023