3,3',5-Triiodo-L-thyronine (T3) is a thyroid hormone.¹It is produced by 5'-monodeiodination of the prohormone thyroxine (T4) in various tissues, including liver and kidney. T3 is an agonist of thyroid hormone receptors TRα and TRβ (K_is = 2.3 nM for both) that modulates diverse biological properties, including metabolism, cardiac function, growth, and redox signaling.^2,3,4,5It also functions as an inhibitor of L-type amino acid transporter 1 (LAT1), inhibiting LAT1-mediated leucine uptake in HEK293 cells when used at a concentration of 10 µM.⁶

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