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Ultrastructural changes in thyroid epithelium during involution of the hyperplastic thyroid gland
O Tachiwaki1, J D Zeligs, S H Wollman
1Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
The American Journal of Anatomy
|September 1, 1990
Summary
Thyroid epithelial cells maintained their protein synthesis machinery during involution after hyperplasia. This process differs significantly from involution in other glands like the prostate or mammary glands.
Area of Science:
- Endocrinology
- Cell Biology
- Histology
Background:
- Thyroid glands can become hyperplastic due to factors like low iodine and antithyroid drugs.
- Understanding the cellular changes during thyroid involution is crucial for comprehending thyroid gland regulation.
Purpose of the Study:
- To investigate the ultrastructural changes in thyroid epithelial cells during the involution of a hyperplastic thyroid gland.
- To compare the involution process in the thyroid with that of other endocrine glands.
Main Methods:
- Male Fischer rats were fed a low-iodine diet with thiouracil to induce thyroid hyperplasia.
- Involution was induced by switching to a high-iodine diet (Purina Laboratory Chow).
- Thyroid ultrastructure was examined via electron microscopy at various time points.
Main Results:
- Organelles involved in thyroglobulin synthesis and secretion (rough endoplasmic reticulum, Golgi apparatus, apical vesicles) remained well-preserved.
- Apical plasma membranes showed irregularity, suggesting rapid discharge of contents into the follicular lumen.
- While small dense bodies (potentially phagosomes) increased, extensive autophagy or lysosome incidence was not observed.
Conclusions:
- Thyroid gland involution involves the maintenance of the protein synthetic apparatus in epithelial cells.
- The involution process in the thyroid gland is distinct from that observed in prostate and mammary glands, characterized by minimal autophagy and cell death.