Abstract
Thyroglobulin (Tg) is believed to be iodinated immediately after secretion of Tg into the follicular lumen. In recent years, however, Tg has reportedly been suggested to be iodinated in follicle cells on the basis of biochemical studies. We encountered a boy with goiter diagnosed at the age of 5.5 years, the pathogenesis of which was considered to be Tg deficiency because of Tg secretion failure in blood.
Results: 1. The Tg level in the patient's thyroid tissue was very low, about 10% of the normal level according to SDS-PAGE. The main band was 19S Tg, and was almost the same as that of the normal control in terms of molecular weight, immunological aspect and electrophoresis. 2. There was no abnormality in the H2O generating system, and thyroid peroxidase activity was higher than that of the normal controls. 3. Electron-microscopic findings: the rough endoplasmic reticulum was markedly dilated. 4. Immunohistological findings: There was homogenous, positive staining for Tg and T4 in the cytoplasm of the follicle cells and follicular cavity in the normal thyroid, while Tg and T4 staining were seen only in the cytoplasm of the folliclar cells in our patient. In conclusion; 1)These observations are compatible with a defect in Tg transport from the cell into the lumen. 2)It might suggest that direct production of T4 from Tg is achieved by intracellular iodination of Tg. Consequently, this patient was considered to have been clinically maintained in a euthyroid state.
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Ohyama, Y., Nakamura, S., Kazahari, K. et al. A CASE OF CONGENITAL EUTHYROID GOITER WITH IMPAIRED THYROGLOBULIN (TG) TRANSPORT: IHHUNOHISTOCHEMICAL EVIDENCE OF INTRACELLULAR TG IODINATION. Pediatr Res 33 (Suppl 5), S91 (1993). https://doi.org/10.1203/00006450-199305001-00529
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DOI: https://doi.org/10.1203/00006450-199305001-00529