Final answer:
T3 and T4 release from the thyroid gland is stimulated by thyroid-stimulating hormone (TSH), which is produced by the anterior pituitary. TSH triggers the production of T3 and T4 from thyroglobulin in the thyroid follicles. T3 is more active than T4 and responsible for most of the effects of thyroid hormones.
Step-by-step explanation:
T3 and T4 release from the thyroid gland is stimulated by thyroid-stimulating hormone (TSH), which is produced by the anterior pituitary. TSH binding at the receptors of the follicle of the thyroid triggers the production of T3 and T4 from a glycoprotein called thyroglobulin. Thyroglobulin is present in the follicles of the thyroid, and is converted into thyroid hormones with the addition of iodine.
T3 has three iodine ions attached, while T4 has four iodine ions attached. T3 and T4 are then released into the bloodstream, with T4 being released in much greater amounts than T3. As T3 is more active than T4 and is responsible for most of the effects of thyroid hormones, tissues of the body convert T4 to T3 by the removal of an iodine ion.