Late effects of brain irradiation on endocrine organs

A single dose of 8 or 20 Gy Co γ rays was given to C3H male mice at 4 months of age. The ultrastructural changes in mouse pituitary, thyroid and the adrenal gland due to brain irradiation were observed at 4 days to 18 months after irradiation. The pituitary microvasculature showed degenerative lesions including swollen endothelial cells and cytoplasmic blebs in the capillary sinusoids of all irradiated animals at 4 days after irradiation and persisted at later times (12-18 months). Cell atrophy, an increase of lysosomal-like bodies in the endocrinal cells and interstitial fibrosis were found in the anterior pituitary at 12 months and became more severe at 18 months after irradiation. The posterior pituitary was more resistant to radiation as compared with anterior lobe. Late degenerative changes were noted in the thyroid gland of all animals after 20 Gy irradiation. These changes included interstitial fibrosis, follicular degeneration, and abnormal thickening of the basement membrane of follicular cells. Focal hyperplasia frequently appeared in the adrenal cortex at 12 and 18 months after irradiation. Many necrotic cells with cytoplasmic vacuolation and severe interstitial fibrosis were observed in the adrenal cortex of all irradiated animals. Cell vacuolation and degranulation were observed in the adrenal medulla at 18 months after irradiation.