Subacute thyroid injury and relative parathyroid preservation following ionizing radiation: altered HSP-90...

Ionizing radiation is widely used in the treatment of head and neck malignancies. However, its subacute effects on adjacent endocrine tissues have not yet been fully elucidated. This study aimed to investigate the structural changes that develop in the thyroid and parathyroid glands following irradiation and to evaluate HSP-90 immunoexpression in these tissues. The researchers initially randomized eighteen male Wistar-Hannover rats into control and irradiation groups (n = 9 per group). Rats in the irradiation group underwent 6-MV photon irradiation of the head and neck target region using a nominal prescribed single-fraction dose of 18 Gy with a Varian Clinac iX linear accelerator. One of the irradiated animals died on day 8; consequently, the day-21 analyses included nine control and eight irradiated animals. On day-21, the researchers performed histopathological examination and immunohistochemical evaluation of HSP-90 immunoexpression in thyroid and parathyroid tissues. Irradiation significantly increased vascular congestion (p = 0.031), inflammatory cell infiltration (p = 0.040), and epithelial desquamation (p = 0.006) in the thyroid tissue compared to the control group. It also significantly reduced HSP-90 immunoexpression in the thyroid follicular cells (p = 0.011). In contrast, irradiation did not cause marked disruption in the tissue architecture of the parathyroid glands. HSP-90 immunoexpression also showed no significant difference between the control and irradiation groups (p = 0.914). A single dose of high-energy photon irradiation induced subacute microstructural damage in the thyroid gland and reduced HSP-90 immunoexpression. The parathyroid gland, however, largely preserved its overall morphology and HSP-90 immunoexpression at day-21. These results indicate that thyroid and parathyroid tissues exhibit organ-specific subacute responses to irradiation.