thīˈräkˌsēn, -_sə̇n noun
also thy·rox·in -_sə̇n
( -s )
Etymology: International Scientific Vocabulary thyr- + ox- + -ine, -in
: a crystalline iodine-containing phenolic amino acid C 15 H 11 I 4 NO 4 that is the chief active principle of the thyroid gland, occurs there in the levorotatory l -form combined in thyroglobulin and in the blood apparently bound to plasma protein, is also made synthetically (as from diiodotyrosine), and is used especially in the form of its soluble sodium salt in the treatment of hypothyroidism; tetraiodo-thyronine — compare thyroid hormone , triiodothyronine