Acute Thyroid Profile Changes During External Beam Irradiation of Neck.

Thyroid gland is irradiated to a considerable dose in conventional radiotherapy of head neck cancer and significant proportion of patients later develop hypothyroidism. This study is an effort to shed light on acute changes in thyroid function after irradiation those are less clearly defined. Values were recorded before radiation treatment, after 4 week of irradiation, after completion of treatment, 1 month after completion of treatment and after 4 months of completion of treatment. A repeated measures ANOVA with a Greenhouse-Geisser correction determined that mean T3, T4 and TSH levels differed statistically significantly between time points. Post hoc test using the Bonferroni correction revealed statistical significance difference in values of T3, T4 and TSH done at specific intervals. External irradiation in cancer therapeutic doses affects thyroid function and sets at a new point with increased TSH, but in reference ranges, to maintain required thyroxin level.