Correlations of urinary iodine level and thyroid function in pregnant women

Objective To investigate the correlations of iodine nutrition status and thyroid function in pregnant women.Methods Three hundred and ninety-tive persons were randomly selected for laboratory testing to evaluate correlative index of iodine nutrition status and thyroid function after the application of universal salt iodization.The levels of iodine in urinary and tap water samples were measured by a spectrophotometer method.The concentration of salt iodine was measured by the method of iodometric titration with sodium subsulfite.The levels of thyroid-stimulating hormone(TSH),free triiodothyronine(FT3)and free thyroxine(FT4)were tested by a chemistry radiation method.Results The median value of urinary iodine was 170.3 μg/L,170.2 μg/L,162.4 μg/L respectively in the women with the 1st,2nd and 3rd timester of pregnancy,which were all significantly lower than that in non-pregnant women( 251.9 μg/L,all P0.05).The lower level of FT4 and FT3 were observed in 8.7%(9/104)and 9.6%(10/104)of women with the 2nd trimester of pregnancy,and in 22.7%(22/97)and 17.5%(17/97)of women with the 3rd trimester of pregnancy,respectively.During the 3rd trimester of pregnancy,36.6%(15/41)of women with thyroid function abnormalities had urinary iodine level higher than 300 μg/L,which was significantly higher than that in those with normal thyroid function(P0.05).Conclusion The pregnant women have good nutritional status of iodine in Hangzhou.The results suggested the importance of thyroid function evaluation for pregnant women with urinary iodine levels lower than 150 μg/L or higher than 300 μg/L.