Nuclear hormone receptor that can act as a repressor or activator of transcription. High affinity receptor for thyroid hormones, including triiodothyronine and thyroxine. Binds DNA as a dimer; homodimer and heterodimer with RXRA (By similarity). Interacts with the coactivators NCOA1/SRC1, NCOA2/GRIP1, NCOA7 and MED1/TRAP220 in a ligand-inducible manner (By similarity). Interacts with the corepressor NCOR1 in absence of ligand. Interacts with C1D (By similarity). Interacts with NR2F6; the interaction impairs the binding of the THRB homodimer and THRB:RXRB heterodimer to T3 response elements (By similarity). Interacts with PRMT2 and THRSP (By similarity). Interacts with TACC1; this interaction is decreased in the presence of thyroid hormone T3 (PubMed:20078863). Composed of three domains: a modulating N-terminal domain, a DNA-binding domain and a C-terminal ligand-binding domain. Belongs to the nuclear hormone receptor family. NR1 subfamily. Truncated N-terminus. Extended N-terminus.