Triiodothyronine reverse

T3 levels in the blood are low with a decreased rate of formation from thyroxine bnt increased conversion of the latter to reverse triiodothyronine (rTs). 

The structural formulas of thyroxine and triiodothyronine as well as reverse triiodothyronine (rT3) are shown in Figure 38-2. 

Burger A, Dinichert D, Nicod P, Jenny M, Lemarchand-Beraud T, Vallotton MB. Effect of amiodarone on serum triiodothyronine, reverse triiodothyronine, thyroxin, and thyrotropin. A drug influencing peripheral metabolism of thyroid hormones. J Clin Invest 1976 58(2) 255-9. 

There was a modest rise in serum TSH concentration when rifampicin was given to a patient previously stabilized on thyroxine replacement (87). Rifampicin is believed to increase the metabolic clearance of both thyroxine and the inactive compound reverse triiodothyronine and in healthy volunteers it reduces circulating concentrations of total and free thyroxine, although in subjects without thyroid disease it has no effect on serum TSH (86). 

The structural formulas of thyroxine and triiodothyronine as well as reverse triiodothyronine (rT3) are shown in Figure 38-2. All of these naturally occurring molecules are levo (L) isomers. The synthetic dextro (D) isomer of thyroxine, dextrothyroxine, has approximately 4% of the biologic activity of the L isomer as evidenced by its lesser ability to suppress TSH secretion and correct hypothyroidism. 

Chopra IJ. Thyroid function tests thyroxine and reverse triiodothyronine measurements. In Abraham GE, ed. Radioassay systems in clinical endocrinology. New York Marcel Dekker Inc, 1981 101-15. 

Meinhold H, Visser T. International survey of the radioimmunological measurement of serum reverse triiodothyronine. Clin Chim Acta 1980 105 343-50. 

L. Friberg, V. Drvota, A. H. Bjelak, Association between increased levels of reverse triiodothyronine and mortality after acute myocardial infarction, Arch Intern Med 162 1388-94 (2002). 

Reverse triiodothyronine rT3 (Figure 15.6) Animal, plant. milk... 

A wide range of serum thyroid hormones (T4, FT4, T3, reverse triiodothyronine (rT3), thyroxine sulfate (T4S)), TSH and thyroid binding globulin (TBG) were analyzed in our studies T4, but not FT4 levels were indicative of hypothyroxinemia (Williams et at, 2004 Simpson et at, 2005). In 23—27 week gestation infants, T4 serum levels decrease to a nadir at 7 postnatal days and fail to increase in 28—30 week infants. This is in marked contrast to 31—34 and 37—42 week term infants, who show an increase in serum T4 levels at day 7 (Williams et al., 2004 Simpson et at, 2005). 

Homeobox-containing genes Levo thyroxine Messenger ribonucleic acid Polymerase chain reaction Retinoic acid Retinoic acid receptor Retinoic acid response elements Reverse triiodothyronine 3,3 -L-diiodothyronine Triiodothyronine... 

Figure 88.2 The possible pathway of maternal-fetal TH metabolism influenoed by excess iodine. Abbreviations T4, thyroxine T3, triiodothyronine T2, 3,3 -L-diiodothyronine rl3, reverse triiodothyronine D1, type 1 iodothyronine deiodinase D2, type 2 iodothyronine deiodinase D3, type 3 iodothyronine deiodinase.

Two hundred milligrams of amiodarone contains 75 mg of iodine. Patients treated with the common daily dose of 200 mg amiodarone, get a load of 7 mg free iodide/ day, which is 35-times the daily recommended iodine dose. Amiodarone is lipophilic and concentrates in adipose tissue, cardiac and skeletal muscle, and in the thyroid (Daniels, 2001). The amiodarone plasma half life is approximately 52 23 days (Hermann, 2004). Typical changes in thyroid function are an increase in serum T4 and reverse triiodothyronine (rT3), and a decrease in serum T3 concentrations related to the inhibition of 5 -deiodinase-activity, resulting in a decrease in the generation of T3 from T4 and a decrease in the clearance of rT3 (Martino et al, 2001) and an inhibition ofT3 receptor binding and action (Daniels, 2001). 

Notes. rTs, reverse triiodothyronine T3, triiodothyronine T4, thyroxine TSH, thyroid-stimulating hormone (thyrotropin). Amiodarone has intrinsic effects on the thyroid and thyroid hormone production besides those related to excessive iodine intake, and this means that it induces thyroid dysfunction more frequently than any other iodine-containing pharmaceutical. 

NHANES US National Health and Nutrition Examination Survey rT3 Reverse triiodothyronine... 

New York Heart Association Receiver operating characteristics Reverse triiodothyronine Sarcoplastic reticulum calcium ATPase... 

Licastro F, Mocchegiani E, Zannotti M, et al. 1992. Zinc affects the metabolism of thyroid hormones in children with Down s Syndrome Normalization of thyroid stimulating hormone and of reversal triiodothyronine plasmic levels by dietary zinc supplementation. Int J Neurosci 65(1-4) 259-268. (Retrieval in progress)... 

Iodine plays a key structural role in the thyroid hormones of humans and other mammals, primarily in the form of T3 (triiodothyronine) and T4 (thyroxine). In such samples precursor forms such as MIT (monoiodotyrosine) and DIT (diiodotyrosine) or isomer forms such as rT3 (reverse triiodothyronine) may also be measured. Iodine accounts for 65% of the molecular weight of T4 and 59% of the T3.15-20 mg of iodine is concentrated in the thyroid and hormones with 70% distributed in other tissues. In the cells of these tissues, iodide enters via the sodium-iodide symporter (NIS). 

Harris, A.R.C., Fang, S.L., Prosky, J., Braverman, L.E. and Vagenakis, A.G. (1978) Decreased outer ring monodeiodination of thyroxine and reverse triiodothyronine In the fetal and neonatal rat. Endocrinology 103 2216. 

A Simple Method for the Simultaneous Analysis of Reverse Triiodothyronine and 3,3 -Diiodothyronine by Mass Fragmentography Using GC-MS. II. Mass Fragmentographic Identification of 3,3 -Diiodothyronine and Reverse Triiodothyronine in Biological Fluids... 

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