Introduction: Carbimazole is a first-line therapy for thyrotoxicosis and is generally well tolerated. Drug-induced liver injury is rare (<1%) and typically presents as cholestatic hepatotoxicity, in contrast to propylthiouracil, which more commonly causes hepatocellular injury. Clinical presentation may mimic obstructive jaundice, and delayed recognition can lead to unnecessary investigations and interruption of definitive thyroid management. : A 70-year-old female with toxic multinodular goiter developed painless jaundice 4 weeks after starting carbimazole 20 mg daily for thyrotoxicosis precipitated by urinary tract infection. She had no prior liver disease or alcohol exposure. Examination revealed isolated icterus without features of chronic liver disease. Initial thyroid function tests showed suppressed thyroidstimulating hormone (<0.01 mIU/L) with markedly elevated free T4 (>100 pmol/L), improving after 4 weeks (free T4 29.1 pmol/L). She subsequently developed progressive jaundice without abdominal pain, fever, pruritus, or encephalopathy. Liver biochemistry demonstrated a cholestatic pattern (R factor 1.1) with conjugated hyperbilirubinemia (peak bilirubin 227 µmol/L), mild transaminitis, and elevated alkaline phosphatase. Imaging, including hepatobiliary ultrasonography, contrast computed tomography, and endoscopic ultrasound, excluded biliary obstruction. Viral, autoimmune, and structural causes were negative. Carbimazole-induced cholestatic jaundice was diagnosed based on temporal association and exclusion of alternatives. Carbimazole was discontinued, ursodeoxycholic acid was initiated, and radioactive iodine therapy was performed, followed by gradual recovery. Conclusion Carbimazole-induced hepatotoxicity (0.1–0.2%) is likely idiosyncratic and not dose dependent. Differentiating drug-induced liver injury from thyrotoxicosis-related liver dysfunction is critical, as restoration of euthyroidism alone may normalize liver enzymes. Diagnosis relies on the exclusion of obstruction and recognition of drug chronology. Early drug withdrawal and multidisciplinary management are essential to prevent progression while ensuring timely definitive therapy.
Thyrotoxicosis ; Cholestasis