Drug Action: How Antithyroid Drugs Work

Antithyroid drugs are used to treat hyperthyroidism, in which the thyroid gland produces excessive quantities of hormones. Active hormones are formed when iodine combines with precursor (inactive) hormone. Antithyroid drugs block this combination, reducing the formation of thyroid hormones.

Before drug

Active thyroid hormone is formed when iodine binds to precursor (inactive) hormones in the thyroid gland.

After drug

The drug prevents iodine binding to precursors, reducing the amount of active thyroid hormone produced.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

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