Thyroid

Synthesis of Thyroid Hormones

1. Thyroglobulin(glycoproteins) is secreted from Follicular cells into the lumen
2. Iodine ion is taken up by Na/I pump
3. Iodine ion is then transported to Apical surface
4. TPO oxidises I- to I2
5. TPO Organifies the TBG-tyrosine to TBG-MIT,DIT
6. TPO couples TBG-MIT,DIT to TBG-T3,T4
7. Endocytosis of TBG-T3,T4 under TSH
8. TBG cleaves by lysosomal enzymes
9. T4,T3 released

graph TD
    subgraph Oxidation
    X[Iodine ion] ==>|Thyroid Peroxidase| X1[I2];
    end
    subgraph Organification
    X ==>Thyroid Peroxidase| X2[MIT,DIT on TGB];
    end
    subgraph Coupling
    X2 ==>|TPO| X3[T3,T4,MIT,DIT on TGB];
    end
    subgraph Endocytosis
    X3 ==>|endocytosis| X3a[TGB is Lysed from T3,T4];
    end
    X3a ==>|into blood| X3b[T3,T4]