• Thyroid hormones exert their actions via intranuclear receptors
  • Enter cells via membrane transporter proteins
  • Bind to intranuclear receptors causing activation and conformation changes
  • Allows binding of the complex to specific “thyroid responsive” sections of DNA, leading to DNA transcription and gene expression

There are to major subtypes of thyroid receptors (TR-α and TR-β) each with their own isoforms:

  • Widely expressed
  • Particularly high expression in cardiac and skeletal muscle
  • Widely expressed
  • Unable to bind hormone
  • Function unclear
  • Brain, liver and kidney
  • Hypothalamus and pituitary