Treatment of Hyperthyroidism: Antithyroid Drugs
Image Source - Antithyroid Drugs
• Antithyroid drugs (ATD)
Methimazole (Tapazole or MMI)
• Radioactive iodine
Which therapy is best is a matter of debate. There is no one best treatment. The choice of therapy largely depends on physician experience and the patient’s preferences. The principal objective is to alleviate the thyrotoxicosis and its attendant symptoms.
• ATDs are chiefly used for long-term treatment of patients with Graves disease
ATDs are preferred for pregnant women, children, adolescents, before surgery, and prior to radioactive iodine therapy
PTU is the preferred drug during pregnancy, lactation, and for thyroid storm
MMI will more rapidly normalize the T4 and T3
PTU is supplied as a 50 mg tablet and the usual starting dose is 100 mg three times a day
MMI is supplied as 5 or 10 mg tablet and the usual starting dose is 30 mg daily.
Factors that determine the speed of recovery
Initial degree of hyperthyroidism
Intrathyroidal stores of T4 and T3, which correlates with the size of the thyroid gland
• Factors that favor a sustained remission after ATD:
Decrease in size of the goiter during therapy
Normal thyroid function tests
Negative tests for thyroid-stimulating immunoglobulin
The presence of HLA-DR4
Duration of antithyroid drug therapy
Amount of the medication needed to control the
• Clinical considerations during ATD therapy
Patients should be seen every 6 weeks if they are not pregnant and every 4 weeks if they are pregnant
Patients are usually euthyroid in 6 to 12 weeks
The dose of ATD should be decreased progressively as the hyperthyroidism subsides
A reasonable rule of thumb is to decrease the dose by 25% to 33% each visit if the free T4 and free
T3 are normal.
The free T4 and free T3 are the best tests to monitor during ATD therapy. The TSH may remain low for months after the free T4 and free T3 are normal.
The dose of ATD is decreased to the lowest dose that maintains the free T4 and free T3 within the normal range.
ATDs are discontinued after 12 to 24 months of control of the hyperthyroidism
Most relapses occur within the first year off the
Rate of recurrent thyrotoxicosis plateaus at 50% at year 5 following discontinuation of the ATD Lifelong follow-up for all patients with Graves disease is essential because hypothyroidism may occur years after successful ATD treatment.