The effect of whole-body irradiation on the T4 and T3 content in blood plasma in preirradiated and non-preirradiated pigs

2 groups of pigs (with 6 animals each) were irradiated with 1.0 Gy or a 9 MeV X-ray of a linear accelerator, followed 30 days later by a second irradiation with 2.5 or 3.0 Gy. For comparison, groups of non-irradiated animals and groups without preirradiation but with a second irradiation dose of 2.5 Gy were used. The content of T4 and T3 in the blood plasma was determined by radioimmunoassay. 1.0 Gy caused a significant increase of the T3 content. After the second irradiation exposure with 2.5 Gy, the content of T4 and T3 in the blood plasma were markedly enhanced in comparison with the hormone level in non-preirradiated animals. Preirradiation with 1.0 Gy improves the ability of the thyroid gland to react towards a higher radiation dose. (author)