Thyroid receptor beta

Figure 6.18. Receptor site of thyroid receptor beta filled with spheres (for sake of clarity, sphere centers are depicted actual size of spheres is larger, so that spheres overlap) and thyronine. Crystal structure taken from the PDB (ID Ibsx).

GurneU, M., and V. K. Chatteijee. 2004. Nuclear receptors in disease Thyroid receptor beta, peroxisome-prohferators-activated receptor gamma and orphan receptors. Essays in Biochemistry 40 169-190. 

O. Bakker, H.C. van Beeren and W.M. Wiersinga, Desethylamiodarone is a noncompetitive inhibitor of the binding of thyroid hormone to the thyroid hormone beta 1-receptor protein, Endocrinology 134(4), 1665-1670(1994). 

S.U. Trost, E. Swanson, B. Gloss, D.B. Wang-lverson, H. Zhang, T. Volodarsky, G.J. Grover, J.D. Baxter, G. Chiellini, T.S. Scanlan and W.H. Dillmann, The thyroid hormone receptor-beta-selective agonist GC-1 differentially affects plasma lipids and cardiac activity, Endocrinology 141(9), 3057-3064 (2000). 

Erion MD, Cable EE, Ito BR, Jiang H, Fujitaki JM, Finn PD, Zhang BH, Hou J, Boyer SH, van Poelje PD et al (2007) Targeting thyroid hormone receptor-beta agonists to the liver reduces cholesterol and triglycerides and improves the therapeutic index. Proc Natl Acad Sci USA 104 15490-15495... 

The reason clenbuterol begins to lose effectiveness after only 2 weeks is that the beta-2-receptors it interacts with are quite sensitive. (These are adrenalgenic receptors) Once these receptors are over stimulated for a prolonged period of time they become insensitive. Oddly enough it appears that DNP and thyroid hormones help regenerate adrenalgenic receptor function. 

Dupre SM, Guissouma H, Flamant F, et al. Both thyroid hormone receptor (TR) beta 1 and TR beta 2 isoforms contribute to the regulation of hypothalamic thyrotropin-releasing hormone. Endocrinology. 2004 145 2337-2345. 

The steroid hormones act on cytoplasmic receptors, and the resulting complex moves to the nucleus to influence DNA transcription of proteins. Thyroid hormone directly enters the nucleus where it alters DNA, causing production of. certain enzymes. A particular chemical may have more than one receptor type (e.g., alpha and beta receptors). Epinephrine, for instance, acts on alpha-1 receptors to produce vasoconstriction, and on beta-2 receptors to produce vasodilation. 

ACTH, adrenocorticotropin a-su, alpha subunit -end, beta-endorphin p-FSH, beta follicle stimulating hormone fS-LH, beta luteinizing hormone -LPH, beta lipotropin -TSH, beta thyroid stimulating hormone, ER, estrogen receptor GH, growth hormone. 

Amiodarone causes microcrystalline deposits in the cornea and skin, thyroid dysfunction (hyper- or hypothyroidism), paresthesias, tremor, and pulmonary fibrosis. Amiodarone rarely causes new arrhythmias, perhaps because it blocks calcium channels and beta receptors as well as sodium and potassium channels. 

Thyroid hormone binds to receptors in the nucleus that control the expression of genes responsible for many metabolic processes. The T3 receptor exists in two monomeric forms alpha and beta. When activated by T3, the a and (3 monomers combine to form ao, PP, or aP dimers. These Tj-activated dimers bind to DNA response elements and control the synthesis of RNA, which codes for specific proteins that mediate the actions of thyroid hormones. 

Beta-adrenoceptor antagonists are used in the treatment of hyperthyroidism to alleviate symptoms but are not considered to influence thyroid hormone production nor the effect of the hormone on cell function. A study of the effect of beta-blockers on lymphocyte metabolism was done with the purpose to clarify their mechanism of action in hyperthyroidism [68]. When hyperthyroid subjects were treated with beta-blockers, lymphocyte heat production was found to be within normal limits, thus showing that beta-blockers prevent the expected increased of cell metabolism under stimulation of thyroid hormone. These results seem to indicate that increased thermogenesis in hyperthyroidism is mediated via adrenergic receptors, rather than via nuclear thyroid hormone receptors. 

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