[Isoform Alpha-1]: Nuclear hormone receptor that can act as a repressor or activator of transcription. High affinity receptor for thyroid hormones, including triiodothyronine and thyroxine. {ECO:0000269|PubMed:12699376, ECO:0000269|PubMed:14673100, ECO:0000269|PubMed:18237438, ECO:0000269|PubMed:19926848}. [Isoform Alpha-2]: Does not bind thyroid hormone and functions as a weak dominant negative inhibitor of thyroid hormone action. . This is the function of ENSG00000126351 (THRA, thyroid hormone receptor alpha).