[Methimazole-induced cholestatic jaundice in a hyperthyroid patient]

Area of Science:

• Endocrinology
• Hepatology
• Pharmacology

Background:

• Hyperthyroidism is a common endocrine disorder managed with antithyroid drugs, surgery, or radioactive iodine.
• Methimazole is a preferred antithyroid medication due to its efficacy and generally mild side effect profile.
• Hepatotoxicity is a rare but serious adverse effect associated with methimazole therapy, often presenting as cholestatic jaundice.

Observation:

• A 33-year-old woman with Graves' disease developed pruritus and jaundice after three weeks of methimazole treatment.
• Initial investigations, including viral hepatitis markers and hepatobiliary ultrasonography, were unremarkable.
• Laboratory tests revealed elevated alkaline phosphatase, total bilirubin, and aminotransferase levels.

Findings:

• Liver biopsy confirmed hepatotoxicity, and the CIOMS scale indicated a highly probable causal relationship with methimazole.
• Discontinuation of methimazole led to clinical improvement within 5 days.
• Normalization of liver function tests was observed within 5 weeks of medication cessation.

Implications:

• This case underscores the importance of monitoring liver function in patients receiving methimazole.
• Early recognition and drug withdrawal are crucial for managing methimazole-induced hepatotoxicity.
• The findings emphasize the need for a thorough diagnostic approach to identify drug-induced liver injury.