The present work is concerned with the histological and histochemical effects of hypervitaminosis D on thyroid and parathyroid glands of the albino rats. The thyroid gland exhibits some variations due to hypervitamino sis D as follow: The follicles appeared swollen and their epithelial lining become flattened. Some follicles showed some degeneration in which the cells lost their boundaries. Some follicles lost their characteristic shape and the follicular cells are hypertrophied showing pyknotic nuclei. The blood vessels become wider. The quantity of collagenous fibers is decreased than the control. The amount of carbohydrates is not changed, but the protein level is increased in immature stages where it is decreased in adult ones.
With respect to the parathyroid gland of treated rats, the following results had been occured: No changes could be observed in immat, e stages of
14-21, and 28-days. In adult rats of 97- and 111-days old, the following changes had been occured: The chief cells are shrinked with deeply stained pyknotic nuclei. Some chief cells are degenerated and lost their characteristic pattern. The connective tissue septa separating the nests of chief cells are increased, and the amount of collagenous fibers is increased. The carbohydrate level is not affected, but the proteinic content is elevated in 14-days old and adult stages than normal.