OBJECTIVETo understand the level of thyroid function and the prevalence of the thyroid diseases of children in high water iodine areas.

METHODTwo primary schools were selected by purposive sampling from Haixing county, Hebei province in April 2010. A total of 371 children were selected from six classes by cluster sampling in the schools. Morning-urine and venous blood (5 ml) were collected to measure the levels of urinary iodine, free triiodothyronine (FT(3)), free thyroxine (FT(4)) and sensitive thyroid-stimulating hormone (sTSH) in serum and to evaluate the iodine status and thyroid function of children.

RESULTSThe median urinary iodine of the children was 1032.08 µg/L. Overall, 96.2% (357/371) of the children's urinary iodine were ≥ 300 µg/L and 68.5% (254/371) were ≥ 800 µg/L. The level of FT(3) and FT(4) were (6.28 ± 0.81) pmol/L and (16.37 ± 2.72) pmol/L, respectively. The median of sTSH was 4.01 mU/L. The FT(4) among boys ((16.63 ± 2.60) pmol/L) was significantly higher than that among girls ((15.99 ± 2.85) pmol/L) (P < 0.05). Overall, 44 subjects were diagnosed as thyroid disease (11.9%), 25 were subclinical hypothyroidism (57% of the total patients), 4 were hypothyroidism (9%), 10 were hyperthyroidism (23%) and 5 were subclinical hyperthyroidism (11%). In the urinary iodine of 200 - 799 µg/L, the prevalence of thyroid disease and hypothyroidism were 6.3% (7/111) and 14.6% (27/254), respectively. When urinary iodine ≥ 800 µg/L, the prevalence of thyroid diseases and hypothyroidism were 3.6% (4/111) and 8.3% (21/254), respectively.

CONCLUSIONMost of the children in high water iodine areas had excessive iodine intake. Levels of the children's thyroid hormone were within the normal range. The prevalence of thyroid disease were high, in these areas and the thyroid disease were mainly the subclinical hypothyroidism.