Effect of low and high doses of carbimazole in the treatment of Grave’s thyrotoxicosis: A prospective, open-label, and observational study

Introduction: Graves’ disease (GD) is an autoimmune disease, characterized by hyperthyroidism, thyroid associated ophthalmopathy, and/or pretibial myxoedema. GD is usually treated by anti-thyroid drug (ATD) as the first line therapy unless contraindicated. However, optimal dose of ATD remains uncertain. Higher doses restore the thyroid hormone level earlier, but they are associated with more side effects. Lower doses are effective in mild form of GD however it may not be much effective in severe form of GD. In spite of regular treatment many patients suffering from GD have deranged thyroid function test. Aim: We conducted this study with aim to see the treatment response of 20 (low) mg and 40 (high) mg per day of CBZ as initial treatment for GD. Materials and Methods: This was a prospective, open label, and observational study conducted on newly diagnosed GD patients. Patients were classified into two groups based on TT4. Patients having TT4 value <20 µg/dl were classified as mild to moderate hyperthyroid patients and TT4 value >20 µg/dl were classified as severe hyperthyroid patients. Mild to moderate and severe hyperthyroid patients were given 20 mg (Group A) or 40 mg CBZ (Group B), alternately. Each patient was reviewed two times, at 4–6 weeks and 8–10 weeks. TT3, TT4, and TSH were measured at each visit along with clinical features. Results: The present study demonstrated that low dose of CBZ is as effective as high dose in restoring thyroid hormone concentration in newly diagnosed hyperthyroid patients. At 4–6 weeks of therapy 86.11% in low dose group and 85.29% in high dose group became euthyroid with treatment. However, at 8–10 weeks of therapy, 86.11% in the low dose group and 61.76% in the high dose group became euthyroid. Conclusion: An initial low (20 mg/day) dose of CBZ is effective in controlling hyperthyroidism in most of the Indian patients, with a low risk of drug related hypothyroidism and hyperthyroidism.