<P> Thyroid hormones are two hormones produced and released by the thyroid gland , namely triiodothyronine ( T ) and thyroxine ( T ) . They are tyrosine - based hormones that are primarily responsible for regulation of metabolism . T and T are partially composed of iodine . A deficiency of iodine leads to decreased production of T and T , enlarges the thyroid tissue and will cause the disease known as simple goitre . The major form of thyroid hormone in the blood is thyroxine ( T ) , which has a longer half - life than T. In humans , the ratio of T to T released into the blood is sometimes claimed to be quite high , but thyroid removal patient data suggests it to vary between 4 : 1 to 2 : 1 , the average being 100 : 36 ( roughly 2.8 : 1 ) . T is converted to the active T ( three to four times more potent than T ) within cells by deiodinases ( 5 ' - iodinase ) . These are further processed by decarboxylation and deiodination to produce iodothyronamine ( T a ) and thyronamine ( T a ) . All three isoforms of the deiodinases are selenium - containing enzymes , thus dietary selenium is essential for T production . Edward Calvin Kendall was responsible for the isolation of thyroxine in 1915 . </P>
<P> Thyroid hormones are two hormones produced and released by the thyroid gland , namely triiodothyronine ( T ) and thyroxine ( T ) . They are tyrosine - based hormones that are primarily responsible for regulation of metabolism . T and T are partially composed of iodine . A deficiency of iodine leads to decreased production of T and T , enlarges the thyroid tissue and will cause the disease known as simple goitre . The major form of thyroid hormone in the blood is thyroxine ( T ) , which has a longer half - life than T. In humans , the ratio of T to T released into the blood is sometimes claimed to be quite high , but thyroid removal patient data suggests it to vary between 4 : 1 to 2 : 1 , the average being 100 : 36 ( roughly 2.8 : 1 ) . T is converted to the active T ( three to four times more potent than T ) within cells by deiodinases ( 5 ' - iodinase ) . These are further processed by decarboxylation and deiodination to produce iodothyronamine ( T a ) and thyronamine ( T a ) . All three isoforms of the deiodinases are selenium - containing enzymes , thus dietary selenium is essential for T production . Edward Calvin Kendall was responsible for the isolation of thyroxine in 1915 . </P>
which body functions are affected by the thyroid ​ hormones t3 ​ ( tri-iodothyronine ) and t4 ​ ( thyroxine )
which body functions are affected by the thyroid ​ hormones t3 ​ ( tri-iodothyronine ) and t4 ​ ( thyroxine )
regulation of metabolism
regulation of metabolism