Question

Action of Methimazole (Tapazole) & Propylthiouracil (PTU)? SATA

A. Given to replace what the thyroid gland cannot produce to achieve normal thyroid levels (euthyroid). They work the same way as thyroid hormones
B. Inhibit the incorporation of iodine molecules into amino acid tyrosine
C. Impede formation of thyroid hormone

Answer 1

Methimazole (Tapazole) and Propylthiouracil (PTU) are antithyroid medications that inhibit thyroid peroxidase, decrease the production of thyroid hormones T4 and T3 by impeding iodination of tyrosine, and are not replacements for thyroid hormones.

Step-by-step explanation:

The action of the antithyroid medications Methimazole (Tapazole) and Propylthiouracil (PTU) is to impede the formation of thyroid hormone in the body. Contrary to the choice 'A' in the question, these medications do not replace thyroid hormones; rather, they work to decrease the production of thyroid hormones (T4 and T3) by inhibiting the thyroid peroxidase enzyme responsible for the iodination of tyrosine and the coupling of iodotyrosines.

This process normally leads to the synthesis of thyroxine (T4) and triiodothyronine (T3), which control the body's basal metabolic rate. Therefore, the correct answers are 'B' and 'C', as these drugs inhibit the incorporation of iodine into amino acid tyrosine and subsequently impede the thyroid hormone formation.