[The structural and functional multiplicity of T3 receptor and its gene]

Thyroid hormone receptor (TR) is encoded by the protooncogene c-erb A. There are multiple TR isoforms such as TR beta 1, beta 2, alpha 1, variant alpha 2 and alpha 3. There is also a related gene, Rev-erb A. TR and steroid hormone receptors consist of a superfamily and have a characteristic domain structure including DNA-binding, ligand-binding and dimerization domains. The expression of TR isoforms is tissue and cell type specific and is regulated by development and hormonal status. TR mRNA and protein concentrations do not always correlate. TR beta 2, which exists in the pituitary, may be important for the regulation of TSH secretion. The functional difference of TR alpha 1 and TR beta 1 is still unclear and physiological significance of the TR variants is unknown.