High affinity receptor for triiodothyronine (T3). Additional isoforms seem to exist. Expression peaks at the climax of metamorphosis. By thyroid hormone. Composed of three domains: a modulating N-terminal domain, a DNA-binding domain and a C-terminal ligand-binding domain. A number of phenolic and phenol compounds can weakly compete with and disrupt triiodothyronine (T3)-binding including 3,3'5-trichlorobisphenol A, triiodophenol, 3,3'-dibromobisphenol A and 3,3'5-tribromobisphenol A. The synthetic estrogen diethylstilbestrol (DES) is not an effective competitor for T3-binding. Belongs to the nuclear hormone receptor family. NR1 subfamily.