Thyroid nodule prevalence among women in areas of high natural background radiation, Karunagappally, Kerala, India.

PURPOSE: Radiation exposure has been reported to cause thyroid nodules. The study area was Karunagapally, which has several areas with high natural radiation levels derived from thorium and its decay products. Since thyroid abnormalities are more common in women, the focus was only on women.

METHODS

The examinations included interview, ultrasonography of the thyroid and serum assays of free thyroxine (FT4), thyrotropin (TSH), and anti-thyroglobulin levels. Cumulative dose during the childhood and lifetime cumulative dose (lagged by 5 years) were estimated.

RESULTS

We examined 524 female residents aged 17-73 years and found 75 cases of solitary solid thyroid nodules. The prevalence of thyroid nodules were 14.1 % (n = 42) in high dose panchayats and 14.5% (n = 33) in low-dose panchayats. In the logistic regression analysis adjusted for age, the prevalence of solitary thyroid nodule was not linearly related to childhood cumulative dose (P for trend = 0.159) and lifetime cumulative dose (P for trend = 0.333). The prevalence of thyroiditis and hypothyroidism was not related to natural radiation exposure. Serum levels of FT4 or TSH were not related to natural radiation exposure.

CONCLUSIONS

The results obtained from the present study do not support the increase of solitary thyroid nodule, thyroiditis or hypothyroidism in relation to high-natural-background-radiation exposure.