L-3,5,3 -Triiodothyronine

Triiodothyronine (3, 5,3-L-triiodothyronine, T3) is a thyroid hormone. It is producedby outer ring deiodination of thyroxine (T4) in peripheral tissues. The biologic activity of T3 is 3-8 times higher than that of T4. T3 is 99.7% protein-bound and is effective in its free non-protein-bound form. The half-life of triiodothyronine is about 19 h. The daily tur nover of T3 is 75%. Triiodothyronine acts via nuclear receptor binding with subsequent induction of protein synthesis. Effects of thyroid hormones are apparent in almost all organ systems. They include effects on the basal metabolic rate and the metabolisms of proteins, lipids and carbohydrates. 

Trichomonas Vaginalis Tricyclic Antidepressants Triiodothyronine 3, 5,3-L-Triiodothyronine... 

Thyroid hormone receptor, T3R 3,5,3 -L- triiodothyronine, T3 hormone RGGTCA IR-0, DR-4, ER-6,8... 

The thyroid gland secretes two hormones, thyroxine (3,5,3, 5 -L tetraiodothyronine) and triiodothyronine (3,5>3 -L-triiodothyronine), which are commonly known as T4 and T3, respectively (Table 52-1). In addition, the thyroid gland secretes small amounts of biologically inactive 3,3, 5 -L-triiodothyronine (reverse T3 [rTa]) and minute quantities of monoiodotyrosine (MIT) and diiodotyrosine (DIT), which are precursors of T3 and T4. The structures of these compounds are shown in Figure 52-1. 

Gross J and Pitt-Rivees R (1952) Identification of 3,5,3 -L-triiodothyronine in human plaeme. Lancet 1 439. 

Of the many thyroxine analogs which have been prepared in a chemically pure form and tested for physiological activity, relatively few have been detected in mammalian tissues. After the isolation of thyroxine in 1915, no other iodinated thyronines were discovered in thyroid tissue until after the advent of radioactive isotopes. 3,5, 3 -L-Triiodothyronine was isolated by Gross and Pitt-Rivers in 1952 and by Roche, Lissitzky, and Michel (1952). The finding of small quantities of 3,3 -diiodothyronine and of 3,3 5 -triiodothyroninc in thyroid tissue has been reported (Roche et al., 1956b), but this observation has not yet been confirmed. 

There has been much speculation that some compound formed in the peripheral tissues might be the active hormone. This speculation has been prompted by the fact that there is usually a latent period of hours or even days before the occurrence of a detectable response to an injection of L-thyroxine. 3,5,3 -L-Triiodothyronine has a considerably shorter latent period than L-thyroxine in man it has therefore been su ested that partial deiodination might produce the peripherally active compound. However, the rate at which, and extent to which, L-thyroxine is converted by the peripheral tissues to L-triiodothyronine is not of sufficient magnitude to lend support to this suggestion (cf. Pitt-Rivers and Tata, 1959). The report by Thibault and Pitt-Rivers (1955) that tetraiodothyroacetic acid and triiodothyroacetic acid have an immediate action on oxidative processes... 

It has been known for some time that a difference between the physiological disposition of 3,5,3 -l-triiodothyronine and that of L-thyroxine probably accounts for the more rapid production of metabolic effects in vivo by the former compound (cf. Van Arsdel et al., 1954). More recently, it has become apparent that the lesser in vivo potency of certain compounds with altered side chains (the n-isomers as well as the acetic and propionic acid analogs of both thyroxine and triiodothyronine) probably results from a lower concentration of these analogs in the peripheral tissues (Larson and Albright, 1958 Tapley et al., 1959 Hatfield et at., 1960, 1961). As an example, the significance of the difference in the physiological disposition of the D- and L-isomers of thyroxine will be briefly considered. 

H. Imura, Inner ring monodeiodination of thyroxine and 3,5,3 -L-triiodothyronine in rat brain. Endocrinology, 109 1619 (1981). 

In Table I are listed the most potent of the various analogs of thyroxine, together with a list of their calorigenic potencies relative to that of L-thy-roxinc. The only analog reported to be more potent than L-thyroxine is 3,5, iV-L-triiodothyronine. However, this finding must be interpreted with some reservation the relative potency of the two ( ompounds is not the same at different time intervals following the injection of the hormone. L-Thyroxine produces in man a response which, after a lag period of from... 

L-3-Iodotyrosine, L-3,5-diiodotyrosine, L-triiodothyronine and L-thyroxine are the most important iodinated phenylpropanoids found in nature. L-3-Iodo-tyrosine and L-3,5-diiodotyrosine are derivatives of L-tyrosine. L-Triiodothyro-nine and L-thyroxine are derived from the chemically related amino acid L-thyronine. 

Common Name 3,5,3 -triiodothyronine L-3-[4-(4-hydroxy-3-iodophenoxy)-3,5-diiodo-phenyl]alanine... 

Thyroxine (3, 5, 3,5-L-teraiodothyronine, T4) is a thyroid hormone, which is transformed in peripheral tissues by the enzyme 5 -monodeiodinase to triiodothyronine. T4 is 3-8 times less active than triiodothyronine. T4 circulates in plasma bound to plasma proteins (T4-binding globulin, T4-binding prealbumin and albumin). It is effective in its free non-protein-bound form, which accounts for less than 1%. Its half-life is about 190 h. 

Hypothyroidism (myxedema) results when there is a breakdown of thyroid hormone production in the thyroid gland. Treatment consists of replacing this hormone with aforementioned drugs. Treatment with levothyroxine, 3,5,3, 5 -tetraiodothyronine, is preferred. Lyothyronin, L-3,5,5 -triiodothyronine, is also used, as is lotrix, a mixture of levothyroxine and levothyronine in a 4 1 ratio. Of the drugs of animal origin, thyroidin and thy-roglobulin (proloid) are used. 

Sodium Liothyronine. Sodium hothyronine [55-06-1] is the sodium salt of L-3,5,3 -triiodothyronine. It is made by the controlled iodination of L-3,5-diiodothyronine. It may be contaminated by starting material or L-T4. The USP assay (49) describes a chromatographic separation specifying 3,5-T2... 

Specificity. The specificity of the assay was evaluated by determining the cross-reaction values for a number of chemically related compounds or metabolites of T4. The cross-reactivity for each of these compounds was expressed as the percentage ratio of the amount of T4 which corresponded to 50% of the zero standard binding divided by the amount of the compound that corresponded to the same level of binding. 3,5-diiodo-L-thyronine, 5,5-diphenylhydantoin and triiodothyronine (T3) were tested and they exhibited cross-reactivity values less than 0.02% except T3 which had a crossreactivity of 1.5%. 

General name of iodine-containing amino acids. The most important members are the thyroid hormones 3,3, 5-triiodo-L-thyronine (Tj, triiodothyronine) and 3,3, 5,5 -tetraiodo-L-thyronine (T4, thyroxine). 

L.W. Gonzales and P.L. Ballard. Identification and characterization of nuclear 3,5,3 -triiodothyronine-binding sites in fetal human lung. J. Clin. Endocrinol. Metab. 53 21-28 (1981). 

H.L. Schwartz and J.H. Oppenheimer. Ontogenesis of 3,5,3 -triiodothyronine receptors in neonatal rat brain dissociation between receptor concentration and stimulation of oxygen consumption by 3,5,3 -triiodothyronine. Endocrinology 103 943-948 (1978). 

H.H. Samuels, F. Stanley and J. Casanova, Depletion of L-3,5,3 -triiodothyronine and L-thyroxine in euthyroid calf serum for use in cell culture studies of the actions of thyroid hormone, Endocrinology... 

B. Yusta Ti Besnard, Y, OrtTz-Caro, A. Pascual, A. Aranda and L. Sarlieve, Evidence for the presence of nuclear 3,5,3 -triiodothyronine receptors in secondary cultures of pure rat oligodendrocytes, Endocrinology 122 in press (1988). 

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