thiouracil

Thiouracil is a heterocyclic organic compound. It is a derivative of uracil, where a sulfur atom replaces one of the oxygen atoms in the pyrimidine ring. Specifically, it is 2-thiouracil. This structural modification gives it distinct chemical properties compared to uracil.

Historically, thiouracil and its derivatives, such as propylthiouracil, were used as medications to treat hyperthyroidism, a condition where the thyroid gland produces too much thyroid hormone. They work by inhibiting the enzyme thyroid peroxidase, which is crucial for the synthesis of thyroid hormones. This inhibition reduces the production of thyroxine (T4) and triiodothyronine (T3).

However, the use of thiouracil as a primary treatment for hyperthyroidism has largely been replaced by other medications like methimazole and propylthiouracil. This is due to a higher incidence of side effects associated with thiouracil itself, including potential bone marrow suppression (agranulocytosis), skin rashes, and liver problems. While still relevant in understanding thyroid hormone synthesis and its inhibition, its direct therapeutic application in humans is now limited. It may still find use in veterinary medicine or in research settings.