[Background] The detection rate of thyroid nodules has reached 19%-68%. It has been recognized that excessive or lack of iodine in drinking water can cause damage to thyroid morphology and function. However, the combined effects of fluoride and iodine in drinking water on thyroid morphology and function are inconsistent in the studies from different regions.

[Objective] This study intends to investigate the detection of thyroid nodules in children with different iodine and fluoride contents in drinking water from Cangzhou, Hebei Province, and to provide preliminary data to explore whether iodine and fluoride contents are associated with the detection of thyroid nodules in children.

[Methods] By the method of multistage stratified cluster sampling, in excess iodine area, deficient iodine area, normal iodine area, excess iodine-fluoride area (the area was further divided into three subgroups), and deficient iodine and excess fluoride area in Cangzhou, the study examined thyroid nodules of local children aged 8-15 years in primary or secondary schools from 1-2 administrative villages by color Doppler ultrasonography.

[Results] A total of 1 859 children were investigated, of which 933 were girls and 926 were boys. There were 248 children in the excess iodine area, 216 in the deficient iodine area, 316 in the normal iodine area, 737 in the excess iodine-fluoride area, and 342 in the deficient iodine and excess fluoride area. There were 869 children aged 8-10 years, and 990 children aged 11-15 years. In the selected areas, the proportion of non-iodized salt consumption in the children's households ranged from 77.9% to 97.6%. Comparison among the excess iodine area, the deficient iodine area, and the normal iodine area showed that there was no significant difference in the detection rate of thyroid nodules of the children aged 8-10 and 11-15 years (χ²=4.270, P=0.118; χ²=5.506, P=0.064), and there was no significant difference in the detection rate of thyroid nodules between the two age groups in the same area (χ²=0.299, P=0.584; χ²=0.000, P=1.000; χ²=0.240, P=0.878). Comparison among the three subgroups in excess iodine-fluoride area showed that there were significant differences in the detection rate of thyroid nodules of children aged 8-10 and 11-15 years (χ²=37.933, P < 0.000 1; χ²=27.385, P < 0.000 1), and the highest detection rates of thyroid nodules in the two age groups were both in the subgroup 1 (23.08%, 29.82%). Comparison between the deficient iodine and excess fluoride area and the deficient iodine area showed that the detection rates of childhood thyroid nodules at the age of 8-10 years were not significantly different (χ²=1.907, P=0.167), but in the group at the age of 11-15 years, the detection rate of childhood thyroid nodules in the former area was significantly higher (7.44%) than the latter (1.75%) (χ²=4.721, P=0.030), and there was no significant difference in the detection rate of thyroid nodules between the two age groups in the same area (χ²=0.235, P=0.627; χ²=1.390, P=0.238).

[Conclusion] In the normal fluoride area with different contents of iodine in water, there is no difference in the detection rate of thyroid nodules among children aged 8-15 years in Cangzhou of Hebei Province. In the excess fluoride-iodine area, the detection rate of thyroid nodules among children aged 8-15 years varies with the content of iodine in water. Compared with the deficient iodine area, the detection rate of thyroid nodules among children aged 11-15 years is higher than that in the deficient iodine and excess fluoride area.

Key Words: drinking water;  iodine;  fluoride;  thyroid nodules;  children