Thyroid Hormone Synthesis

  • Active transport of iodine (I-) into the thyroid follicular cells:
    • Is mediated by the Na/I symporter (NIS)
  • Intracellular accumulated iodide ion is then passively translocated across the apical membrane into the colloid:
    • Via pendrin proteins and Cl channels
  • The effluxed iodide ion becomes covalently attached to thyroglobulin:
    • Mediated by thyroperoxidase (TPO)
  • Further iodinization of tyrosine molecules on the thyroglobulin glycoprotein then occurs via TPO forming:
    • Monoiodotyrosines (MIT) and diiodotyrosines (DIT):
      • Which are then coupled to create the bioactive thyroid hormones T4 and T3:
        • Again catalyzed via TPO
  • Colloid is taken up into the follicular cell by:
    • Micropinocytosis
  • Through digestion of this thyroglobulin by:
    • Lysosomal extracts and a resulting proteolytic breakdown of the thyroglobulin:
      • T4 and T3 are released into the cytoplasm
  • Finally T4 and T3 are transported into the circulation by a hormone transporter:
    • Monocarboxylate transporter 8 (MCT8)

#Arrangoiz #ThyroidSurgeon #CancerSurgeon #HeadandNeckSurgeon #EndocrineSurgeon #ThyroidHormone

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