YODTIRONINA — the components of specific protein of a thyroid gland of thyreoglobulin participating in synthesis of its hormones; the iodated derivative amino acids of a tironin.
are among 3,3 '-diyodtironin (T2), 3,3', 5 '-triiodothyronine (T3'), 3,5,3 '-triiodothyronine (T3) and 3,5,3', 5 '-tetrayodtironin, or thyroxine (T4) — see a formula. Y. are formed in a molecule of thyreoglobulin at condensation of molecules iodtyrosines (see). They cannot be formed at simple iodination of thyreoglobulin as Yodtirozina, their biosynthesis — complex process, the mechanism to-rogo even is completely not found out. In composition of thyreoglobulin from Y. the thyroxine containing apprx. 20 — 30% of all connected iodine and a small amount 3,5,3 '-the triiodothyronine containing 3 — 4% of iodine enter generally (see. Triiodothyronine ); others Y., as a rule, are not found neither in a hydrolyzate of a thyroid gland, nor in blood. All natural Y., being in structure thyreoglobulin (see) and in free consisting scientific research institute in blood, treat 1 row. Y. are released from thyreoglobulin in a thyroid gland at hydrolysis by proteolytic enzymes and come to a blood flow. In blood Y. contact specific proteinaceous carriers and in such look are transported to peripheral fabrics.
Tiroksin (see) and triiodothyronine — the main hormones of a thyroid gland having versatile effect on a metabolism; The T3 influences metabolism 5 — 10 times more active than T4. In the conditions of iodic insufficiency there is compensatory strengthening of products of T3 directed to maintenance of an euthyroid state.
Y. whether are defined in a hydra but a thyroid gland and in blood by radiokhromatografichesky methods after preliminary introduction of a radioiodine or radioimmunnol. by methods. In a wedge, practice for assessment of function of a thyroid gland in blood determine content proteinaceous and connected iodine (see) or butanolekstragiruyemy iodine (see), reflecting contents Y. in blood.
«the competitive analysis» — a method of definition in blood Y was widely used., based on the competitive relation investigated and marked Y. (T3, T4) in the course of linkng with specific proteins of a blood plasma.
Strengthening of products Y. leads to development thyrotoxicosis (see), decrease — hypothyroidism (see). Indicators of the proteinaceous and connected iodine normal make 3,5 — 8,5 mkg of %, at a thyrotoxicosis — it is higher than 8,5 mkg of %; indicators of the proteinaceous extracted iodine on 0,5 — 1,0 mkg of % are lower than proteinaceous and connected.
See also Iodic exchange .
Bibliography: Thyroid hormones, under the editorship of. I. X. Turakulova, Tashkent, 1972.
I. X. Turakulov.