A 30-year-old pregnant woman and her 2-year-old child are residing in high altitude area. The child is sho in stature, has a potbelly and enlarged protruding tongue, and is developmentally delayed. Iodine is prescribed for mother and child, with the hope of preventing mental retardation in the developing fetus. All are true about oxidation of iodide except
Conversion of iodide ions to an oxidized form of iodine, either nascent iodine (I0) or I3-, which is then capable of combining directly with the amino acid tyrosine. This oxidation of iodine is promoted by the enzyme peroxidase and its accompanying hydrogen peroxide, which provide a potent system capable of oxidizing iodides. Iodide exit from the thyrocyte across the apical membrane to access the colloid is mediated by a Cl-/I- exchanger known as pendrin. The mechanism of action of propylthiouracil is paly to block the peroxidase enzyme that is required for iodination of tyrosine and paly to block the coupling of two iodinated tyrosines to form thyroxine or triiodothyronine. Reference: Guyton; 13th edition; Page no: 953, 960Reference: Ganong's Review of Medical Physiology; 25th edition; Page no: 339
Conversion of iodide to iodine
Promoted by enzyme peroxidase
Iodide transpoed to follicular lumen by Na-I sympoer
Propylthiouracil blocks this step
Nervous system