wt r tetraiodothyronine n T3 ?
T3 & T4 are Triiodothyronine & tetraiodothyronine respectively. These are consider together under the designation thyroid hormone. T3 contains 3 atoms of iodine whereas T4 contain 4 atoms of iodine. T3 is more active & potent than T4 but it is secreted in smaller amounts. T4 can be converted into T3 by the removal of one iodine atom. These are synthesized by follicular cells of thyroid gland by attaching iodine to the amino acid tyrosine under the influence of thyroid stimulating hormone.