A Case Report on Methimazole-Induced Cholestatic Jaundice in an Elderly Man With Hyperthyroidism

Background: The early detection and diagnosis of the causes of jaundice in a hyperthyroid patient taking antithyroid medications are paramount for the appropriate management of these patients. Clinical Case: A 72 year old male is admitted due to septic shock secondary to pneumonia and funguria, acute kidney injury secondary to sepsis, type 2 diabetes mellitus, uncontrolled and Graves’ disease with thyroid nodules (Tirads 4). On physical examination, he has icteresia and generalized jaundice. Methimazole was started 12 days ago. Initial tests were consistent with a cholestatic pattern of jaundice: slightly elevated alanine aminotransferase 70 U/L (16-63), aspartate aminotransferase 84 U/L (15-37) and significantly elevated alkaline phosphatase 662 U/L (46-116), total bilirubin 12.16 mg/dl (0.20-1.0), conjugated bilirubin 11.29 mg/dl (0-0.20) and unconjugated bilirubin 0.87 mg/dl (0-0.80). He has hypoalbuminemia and normal prothrombin time. He has negative anti-Smith antibody, anti-ribonucleoprotein, anti-mitochondrial antibody, and positive anti-nuclear antibody 1:160 speckled pattern. Hepatitis Profile showed chronic hepatitis A infection. Upper Abdomen Ultrasound showed ill-defined border in the left hepatic lobe; intrahepatic ducts and common bile duct are not dilated; gallbladder is contracted with no evident intraluminal echoes. Whole Abdomen with 4-phase Dynamic Liver CT Scan showed multiple ill-defined hypoattenuating lesions in the entire liver parenchyma; intrahepatic ducts, common bile duct, and pancreatic duct are not dilated; and gallbladder is normal in size without intraluminal calculus with possible metastases at spleen, left adrenal gland and tail of pancreas. He has normal AFP and elevated CEA. Methimazole was discontinued at admission and was started on Hydrocortisone 100 mg/IV every 8 hrs. Repeat liver profile panel showed decreasing trends after 4 days of holding methimazole. Repeat fT4 after 6 days of high dose hydrocortisone showed a decrease from 3.09 ng/dl to 1.98 ng/dl (0.89-1.76). Hydrocortisone was continued and tapered accordingly. Plans for RAI discussed. Conclusion: This case emphasizes the need to be vigilant for the very rare but serious adverse events of antithyroid medications.