Thyroid Hormone Receptor - Isoforms

Isoforms

There are three forms of the thyroid hormone receptor designated alpha-1, beta-1 and beta-2 that are able to bind thyroid hormone. There are two TR-α receptor splice variants encoded by the THRA gene and two TR-β isoform splice variants encoded by the THRB gene:

• TR-α1 (widely expressed and especially high expression in cardiac and skeletal muscles)
• TR-α2 (homologous with viral oncogene c-erb-A, also widely expressed but unable to bind hormone)
• TR-β1 (predominately expressed in brain, liver and kidney)
• TR-β2 (expression primarily limited to the hypothalamus and pituitary)