Final answer:
T3 is converted to T4 in the tissues of the body by removing an iodine ion. T3 is more active and responsible for the effects of thyroid hormones. T3 and T4 become attached to transport proteins in the bloodstream.
Step-by-step explanation:
T3 and T4 are thyroid hormones that are produced in the follicles of the thyroid gland. TSH stimulates the production and release of these hormones. The conversion of T4 to T3 occurs in the tissues of the body, where an iodine ion is removed from T4. This conversion is important because T3 is more active and responsible for most of the effects of thyroid hormones. The released T3 and T4 become attached to transport proteins in the bloodstream and are only released when blood levels of unattached hormone decline.