Question 253

Question:

An investigator studying the synthesis of thyroid hormones has developed a transgenic animal deficient in thyroid peroxidase. Within the thyroid gland of this animal, which of the following is most likely to be inhibited?

Correct Answer: C.  Iodide oxidation and binding to tyrosine in the follicle lumen

Thyroid peroxidase is the enzyme responsible for iodide oxidation and binding to tyrosine in the follicle lumen.
The other steps in thyroid synthesis including cleavage of iodine from iodinated tyrosines, endocytosis of colloid, movement of iodide from plasma into thyroid cells, and separation of thyroxine from thyroglobulin in lysosomes, do not require thyroid peroxidase and would therefore not be inhibited in the transgenic animal.