Longitudinal study on the correlations of thyroid antibody and thyroid hormone levels after radiotherapy in patients with nasopharyngeal carcinoma with radiation-induced hypothyroidism.

BACKGROUND The purpose of this study was to evaluate the correlations of thyroid antibody and thyroid hormone in postradiotherapy (post-RT) patients with nasopharyngeal carcinoma (NPC). METHODS Serum thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), thyroperoxidase antibody (anti-TPO), and thyroglobulin antibody (anti-TG) levels of 55 patients with NPC were taken before RT and at 3, 6, 12, and 18 months after RT. Patients with hypothyroidism at 18 months after RT and those with normal thyroid function were categorized into the hypo and normal groups, respectively. The thyroid antibody levels were compared between the 2 groups, and the correlations of thyroid antibody and thyroid hormone were evaluated for the hypo group. RESULTS The anti-TPO and anti-TG of the hypo group were higher than the normal group. In the hypo group, there was a positive correlation (r = 0.51) between TSH and anti-TG and a negative correlation between fT4 and anti-TPO (r = -0.55). CONCLUSION There were correlations of the thyroid antibody and thyroid hormone levels in patients with radiation-induced hypothyroidism.