Pishtaz - Model PT-FT4-96 - Thyroid Elisa Kit - Brochure

Thyroxine hormone is synthesized in thyroid gland which is most important component of endocrine system. Over than 99% of thyroxine (T4) circulates in blood is bound to carrier proteins; thyroxine-binding globulin (TBG), albumin and prealbumin. However, only the free (unbound) portion of T4 is responsible for the biological action. Furthermore, the concentrations of the carrier proteins are altered in many clinical conditions, such as pregnancy. In normal thyroid function as the concentrations of the carrier proteins alters, the total T4 level changes whereas the free T4 concentration remains constant. Thus, measurements of free T4 concentration correlate more reliably with clinical status than total T4 levels. The increase in total T4 levels associated with pregnancy, oral contraceptives and estrogen therapy result in higher total T4 levels while the free T4 concentration remains basically unchanged.