Thyroid hormone receptor alpha; Thyroid hormone receptor beta (TRα; TRβ)

Thyroid hormone receptors alpha and beta are members of the nuclear receptor superfamily that function as ligand-activated transcription factors for thyroid hormones, notably triiodothyronine (T3) and thyroxine (T4)[1][3][5]. Encoded by the THRA and THRB genes, respectively, these receptors are widely expressed and exist in several isoforms due to alternative splicing, with tissue- and developmental stage-specific patterns of expression[1][3][6]. Upon binding their ligand, these receptors regulate gene expression involved in metabolism, cardiac function, neural development, energy expenditure, cholesterol metabolism, and feedback regulation of thyroid axis hormones[1][2][3][4][5][6]. TRα is more prominent in heart, brain, and muscle, while TRβ predominates in liver and pituitary[3][6]. Agonists and selective modulators are used for hypothyroidism, dyslipidemia, and investigational therapies; unselective activation risks off-target effects, particularly cardiovascular complications[5][6]. Mutations in these receptors cause resistance to thyroid hormone syndromes and are implicated in a variety of metabolic and developmental disorders[6].

Other names

TRα (THRA)TRβ (THRB)c-erbA-alphac-erbA-betaNuclear receptor subfamily 1 group A member 1 (NR1A1) [for TRα]Nuclear receptor subfamily 1 group A member 2 (NR1A2) [for TRβ]Thyroid hormone nuclear receptor alpha/betaT3 receptor

Agonists (activate gene transcription via receptor binding for metabolic, cardiovascular, and developmental effects) Selective TRβ agonists lower serum cholesterol by activating TRβ in the liver without significant cardiac stimulation Modulators may repress or activate gene transcription by affecting receptor-coregulator complexes Antithyroid drugs lower hormone synthesis, thus decreasing receptor activity indirectly