Gravesβ hyperthyroidism: In a randomized 12-week study of untreated patients, methimazole normalized FT4 in 96.5% of patients at 30 mg/day and 86.2% at 15 mg/day, compared with 78.3% for propylthiouracil at 300 mg/day. Reported adverse effects were also more frequent with propylthiouracil: 51.9% versus 30.0% with higher-dose methimazole and 13.9% with lower-dose methimazole. These results favor methimazole in the studied population, but the study excluded some patients with severe complications and was limited to short-term biochemical outcomes.
Important safety qualification: Methimazole and carbimazole can rarely cause serious liver injury; the supplied reports document severe cholestatic hepatitis after methimazole in one patient and cholestatic hepatitis with agranulocytosis after carbimazole in another. Case reports establish possibility, not frequency or comparative risk.
Hypothyroidism: The supplied evidence contains only a single case report involving levothyroxine plus liothyronine, so it cannot establish that combination therapy is superior to levothyroxine alone.
Bottom line: The question is underspecified. The most defensible evidence-based statement is: methimazole has the strongest direct support among the provided medicines for typical Gravesβ hyperthyroidism, but no βbest thyroid medicineβ can be selected without knowing the exact thyroid disorder and clinical context. This evidence does not justify self-treatment or a universal drug recommendation.
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