Propylthiouracil mechanism of action?

How does propylthiouracil work in the body?

Propylthiouracil (PTU) treats hyperthyroidism by lowering thyroid hormone production. It does this in two main ways: it blocks thyroid hormone synthesis and it reduces the conversion of T4 (thyroxine) into the more active T3 (triiodothyronine). [1]

What steps does PTU block to reduce thyroid hormones?

PTU inhibits thyroid peroxidase (TPO), the enzyme needed for key steps in making thyroid hormones inside the thyroid gland. By inhibiting TPO, PTU reduces the formation of T3 and T4, which lowers circulating thyroid hormone levels. [1]

How does PTU affect T4-to-T3 conversion?

Beyond blocking synthesis, PTU also inhibits an enzyme involved in converting T4 to T3 in peripheral tissues (outside the thyroid), which further decreases active T3 levels. This contributes to a faster drop in thyroid hormone activity compared with drugs that only block synthesis. [1]

How does PTU’s mechanism relate to why it’s used?

Because PTU reduces both hormone production (via TPO inhibition) and peripheral activation (T4 to T3 conversion), it can rapidly improve the biochemical and clinical picture of hyperthyroidism while the underlying thyroid overactivity is controlled. [1]

Source

[1] https://en.wikipedia.org/wiki/Propylthiouracil