What is it about?
Ahmed R.G., 2018. Genomic actions of thyroid hormones during development. ARC Journal of Diabetes and Endocrinology 4(1), 5-8. DOI: http://dx.doi.org/10.20431/2455-5983.0401002 Thyroid hormones (THs) exhibit crucial activities during the development via the nuclear and extranuclear actions. Genomic actions of THs have been found inside the nucleus. THs (3,5,3'-triiodothyronine (T3) and T4) arrive to the cell via transporter such as the organic anion transporter family (OATPs) and monocarboxylate transporter 8 (MCT8). Then, deiodinases (DI, and II) convert T4 (inactive form) to T3 (active form). At that point, T3 binds to thyroid receptors (TRs; TRα and TRβ), that stimulate transcription by binding, generally as heterodimers with the retinoid X receptor (RXR), to TH response elements (TREs) situated in regulatory regions of target genes. Its activity is controlled by an exchange of corepressor (CoR) and coactivator (CoA) complexes. Negative TREs (nTRE) can facilitate ligand-dependent transcriptional repression. TRs can also adjust the actions of genes that do not comprise a TRE via cross-talk with other transcription factors (TF) that modulate target gene expression. Both co-regulators and receptors are goals for phosphorylation by signal transduction pathways motivated by hormones and growth factors. The nuclear actions of T3 are sensitive to inhibitors of transcription and translation and have a latency of hours to days. Thus, the genomic action of THs can show significant roles during the cellular proliferations and differentiations. A better understanding of these mechanisms would also permit us to refine the timing and dosage of the increase in levothyroxine (L-T4) therapy in hypothyroid pregnant women and to establish whether T4 on its own is indeed the best form of TH replacement in pregnancy. Further studies are required to recognize the crosstalk between THs, their genomic actions and growth factors during the development.
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Why is it important?
The genomic action of THs can show significant roles during the cellular proliferations and differentiations.
Perspectives
A better understanding of these mechanisms would also permit us to refine the timing and dosage of the increase in levothyroxine (L-T4) therapy in hypothyroid pregnant women and to establish whether T4 on its own is indeed the best form of TH replacement in pregnancy. Further studies are required to recognize the crosstalk between THs, their genomic actions and growth factors during the development.
Full Professor Ahmed R. G.
Division of Anatomy and Embryology, Zoology department, Faculty of Science, Beni-Suef University, Egypt.
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This page is a summary of: Genomic Actions of Thyroid Hormones during Development, ARC Journal of Diabetes and Endocrinology, January 2018, ARC Publications Pvt Ltd.,
DOI: 10.20431/2455-5983.0401002.
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