Thyroid hormone receptor alpha (TR-alpha) (TR-alpha)

Thyroid hormone receptor alpha (TR-alpha) is a nuclear receptor and ligand-dependent transcription factor encoded by the THRA gene that mediates the biological effects of thyroid hormones, primarily triiodothyronine (T3). It is widely expressed throughout the body, with particularly high levels in the heart, skeletal muscle, bone, and central nervous system (UniProt P10827). TR-alpha plays a fundamental role in regulating basal metabolic rate, thermogenesis, and the development of the skeletal and nervous systems (NCBI Gene 7067). In the cardiovascular system, it is the dominant isoform responsible for the chronotropic and inotropic effects of thyroid hormones, making it a key regulator of heart rate and contractility (PubMed PMID: 22334611). Mutations in the THRA gene lead to Resistance to Thyroid Hormone alpha (RTHα), a clinical syndrome characterized by growth retardation, skeletal abnormalities, and bradycardia (PubMed PMID: 24659601). While many synthetic thyroid mimetics are designed to be TR-beta selective to avoid cardiac side effects, TR-alpha remains the primary target for standard hormone replacement therapies like levothyroxine. However, excessive activation of TR-alpha can lead to significant safety concerns such as tachycardia and reduced bone mineral density.

Other names

THRANR1A1c-erbA-1Thyroid hormone receptor alpha 1Thyroid hormone receptor alpha 2ERBA1EAR7

Acts as a ligand-activated transcription factor that binds to thyroid hormone response elements (TREs) in the DNA; upon binding triiodothyronine (T3), it undergoes a conformational change that releases co-repressors and recruits co-activators to modulate the expression of target genes (UniProt P10827).