Which drugs are PTU and methimazole used for?

• A. Inhibit thyroid hormone synthesis in hyperthyroidism
• B. Inhibit PTH synthesis
• C. Inhibit calcitonin release
• D. Stimulate insulin secretion

Answer: (A)

These drugs are antithyroid medications used to treat hyperthyroidism by stopping the thyroid from making hormone. They work by inhibiting thyroid peroxidase, the enzyme that catalyzes the iodination of tyrosine residues and the coupling of iodotyrosines inside the thyroid gland. When this synthesis step is blocked, less T3 and T4 are produced, so the body's metabolic rate and thyrotoxic symptoms calm down.

PTU and methimazole are not about affecting PTH, calcitonin, or insulin secretion. They don’t stimulate insulin release or alter calcium- or bone-related hormones; their main action is to reduce thyroid hormone production. While PTU can also reduce conversion of T4 to the more active T3 in the periphery, the primary therapeutic effect you’re aiming for is decreased thyroid hormone synthesis in conditions like Graves disease or toxic goiter.