Profound Hypothyroidism 21 Days After Methimazole Initiation in a Patient With Graves’s Disease and Liver Cirrhosis

Introduction: Methimazole is the first line treatment of nonpregnant Grave’s disease (GD) patients with Grave’s ophthalmopathy. It usually results in euthyroidism within 4 to 12 weeks, and it is recommended to check FT4 every 4 to 6 weeks after initiation of therapy. We report a patient with GD who developed profound hypothyroidism 21 days after starting methimazole. Clinical Case: 51-year-old male with decompensated EtOH/NASH liver cirrhosis, Gilbert’s syndrome, and GD presented with severe hypothyroidism 21 days after initiating methimazole treatment. He initially presented to the emergency department (ED) with atrial fibrillation with a HR of 140 and found to have bilateral exophthalmos and lid lag. Labs: TSH <0.01 uIU/L (normal range (nl) 0.27-4.20), FT4 2.6 ng/dl (nl 0.7-1.7), TT4 6.2 ug/dl (nl 4.5-12), TT3 125 ng/dl (nl 71-180), TBG 14 ug/ml (nl 13-39), TSI 344 IU/l (nl 0-0.5), AST 55 IU/L (nl 14-44), ALT 27 IU/L (nl 9-57), Alk Phosphatase 497 IU/L (nl 45-129), Tbili 7.1 mg/dl (nl 0.2-.1), and albumin 2.1 g/dl (nl 3.4-5). He was started on methimazole 40 mg daily and propranolol 20 mg BID. Three days later, FT4 decreased to 1.3 ng/dl, so methimazole was decreased to 20 mg day. Ten days later, FT4 was 0.2 ng/dl and methimazole was reduced further to 10 mg daily. Eight days later, he presented to the ED with severe lethargy and found to have HR of 38 and oral temperature (T) of 94. TSH was 3.49 uIU/L and FT4 <0.1 ng/dl. Sixteen hours after 200 mcg IV levothyroxine, he had normal mental status, HR of 49, and T of 97.9. FT4 increased to 0.5 ng/dl within 48 hours of thyroxine initiation. Urine drug screen was only positive for tetrahydrocannabinol and other work up for severe lethargy and hypothermia was unremarkable. He was discharged on 100 mcg of PO levothyroxine. Conclusion: Only 21 days after starting methimazole, the patient developed severe lethargy associated with hypothermia, bradycardia, and undetectable FT4, with no alternative etiology and prompt response to IV levothyroxine, consistent with profound hypothyroidism. Although the half-life of T4 is shortened in hyperthyroidism, the particularly fast and profound effect of methimazole in this patient was unusual and likely due to a limited extra-thyroidal pool of thyroxine caused by low TBG level. As cirrhosis is usually associated with increased TBG level, he may have a contributing congenital etiology. Reduced levels of other T4 binding proteins, albumin and pre-albumin may also have contributed. Although methimazole clearance can be decreased in liver impairment, no dose adjustment is generally recommended, and even this would not have explained the observed rapid decrease in FT4 level. Methimazole should be used with caution and FT4 should be checked early and more frequently when treating hyperthyroid patients with liver disease and possible alteration in thyroid binding proteins.