Thyroid hormone receptor beta (TR-beta) is a nuclear hormone receptor for triiodothyronine. It is one of the several receptors for thyroid hormone, and has been shown to mediate the biological activities of thyroid hormone. Knockout studies in mice suggest that the different receptors, while having certain extent of redundancy, may mediate different functions of thyroid hormone. Defects in this gene are known to be a cause of generalized thyroid hormone resistance (GTHR), a syndrome characterized by goiter and high levels of circulating thyroid hormone (T₃-T₄), with normal or slightly elevated thyroid stimulating hormone (TSH). Several transcript variants have been observed for this gene, but the full-length nature of only one has been observed so far.