SUN-353 - A Hard Pill to Swallow: When Malabsorption Spirals into Myxedema Coma

A 27-year-old woman with Hashimoto’s hypothyroidism, papillary thyroid carcinoma s/p thyroidectomy (2018) and radioactive iodine (2019), secondary adrenal insufficiency, and gastroparesis with GJ tube dependence presented with several days of J-feed intolerance and brain fog. For a month, she had progressive nausea, vomiting, diarrhea, left lower quadrant abdominal pain, fatigue, lightheadedness, myalgias, leg swelling, chills, night sweats, and 18-lb weight loss. At home, she recorded temperatures to 95°F and hypotension to 70/50. She previously had 3 episodes of myxedema coma and persistent hypothyroidism despite liquid levothyroxine and triiodothyronine, and she transitioned to IM levothyroxine due to malabsorption from gastroparesis. Medications included albuterol PRN, aprepitant, diphenhydramine PRN, dronabinol, esomeprazole, fluticasone/umeclidinium/vilanterol, hydrocortisone, hyoscyamine PRN, levothyroxine, midodrine, promethazine PRN, and pyridostigmine. Family history included maternal hypothyroidism and thyroid cancer. She lives at home with her husband, uses medical marijuana several times weekly, and does not use alcohol or tobacco. Two weeks prior, TSH was >150 and her endocrinologist advised her to seek IV treatment, but she declined until symptoms worsened.

In the ED, vitals showed temperature 94.3°F, BP 89/54, HR 58, RR 16, SpO2 99% on room air. Exam showed somnolence but intact orientation, clear lungs, regular heart rhythm, soft abdomen with LLQ tenderness, clean GJ site, no edema or rashes, full strength, and no focal neurologic deficits. CT abdomen/pelvis was unremarkable. Labs showed TSH 465, free T4 < 0.10, ACTH 13, AM cortisol 7. ACTH stimulation test rose from 1→6→9 µg/dL. Endocrinology recommended IV hydrocortisone 50 mg q6h and IV levothyroxine 200 mcg daily ×3 days, then 100 mcg daily. Her mentation, nausea, and energy improved with therapy. After one week, TSH improved to 159 and free T4 to 0.95. She was discharged on IV levothyroxine 100 mcg daily with close endocrine follow-up and plans for a levothyroxine absorption study.

This case illustrates how symptoms of severe hypothyroidism can overlap with adrenal insufficiency, chronic GI disease, and malnutrition. Her presentation was precipitated by tube feed intolerance, highlighting how GI dysfunction both manifested with severe hypothyroidism and prevented adequate thyroid hormone absorption. A levothyroxine absorption test can distinguish true malabsorption from non-adherence in patients with refractory hypothyroidism by giving a single large oral dose of levothyroxine followed by serial measurements of thyroid hormone levels over 4-6 hours. This case reinforces that persistent biochemical hypothyroidism with ongoing symptoms should prompt clinicians to consider IV levothyroxine earlier, not only as rescue therapy but as necessary chronic treatment in select patients.

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