Thiouracil

noun

1. A white crystalline compound, C4H4N2OS, that interferes with the synthesis of thyroxine, used to reduce the action of the thyroid gland, especially in the treatment of hyperthyroidism.
2. Any of a class of heterocycles based on 2-thioxo-1H-pyrimidin-4-one; the parent compound interferes with the synthesis of thyroxine and is used in the treatment of hyperthyroidism
3. depresses the function of the thyroid gland