Study On The Relationship Between Iodine Nutritional Status And Hypothyroidism In Pregnant Women In Qingdao Area

Objective:To investigate the urinary iodine level and the thyroid function of pregnant women in Qingdao, to explore the relationship between the iodine nutritional status and hypothyroidism.Methods:663pregnant women who in obstetric clinical of the affiliated hospital of Qingdao University for routine prenatal care were collected from December2011to July2013, and at the same time198non-pregnant women with matched age were collected as the control group. The urinary iodine concentration and thyroid function were measured.(1)According to the iodine nutritional criteria of general population and pregnant women made by WHO, pregnant women were separated to different groups: iodine deficient, iodine adequate, iodine more than adequate and iodine excessive. We got the frequency distribution proportion of different groups and different pregnancy periods, and compared different groups;(2)We observed the physiological changes of thyroid function of different periods, and evaluated the prevalence of hypothyroidism of the pregnant women with pregnancy specific reference ranges of thyroid function, and analyzed the relationship between the prevalence and the urinary iodine level;(3)We analyzed the relationship between the iodine nutritional status and serum TSH,FT4, the prevalence of subclinical hypothyroidism in first trimester of pregnancy;(4) Analyzing the relationship between the urine iodine level and TPOAb,the prevalence of hypothyroidism;(5)Analyzing the relationship between gestational age and the prevalence of hypothyroidism.Results:(1)The median of urine iodine of pregnant women was161.59μg/L, and the ratios of iodine deficient, iodine adequate, iodine more than adequate and iodine excessive groups were44.95%、34.09%、5.69%、5.28%,and the ratio of urine iodine less than100μg/L was19.16%(less than50%),less than50μg/L was3.77%(less than20%);(2)The median of urine iodine in the T1,T2,T3period were175.02μg/L,154.68μg/L,144.38μg/L respectively, and the ratios of iodine deficient of T1,T2,T3period were38.13%、47.62%、53.57%. The ratios of iodine deficient of T2, T3period were higher than T1period(P<0.05;P<0.01),and the urine iodine level of T2,T3period were lower than T1period(P<0.05;P<0.01), and that was no difference between T2and T3period;(3)The thyroid function changed with the increasing pregnancy periods. The serum TSH at T1period was lower than non-pregnant women (P<0.01), and increased with pregnancy periods.At T2,T3periods it was higher than T1period(P< 0.05,<0.01),and it was no difference between T2and T3period;The serum FT4,FT3increased at T1period,than decreased. At T2and T3period it was lower than non-pregnant women (P<0.01),and there was significant difference between three periods(P <0.01;P<0.05);(4)The prevalence of overt hypothyroidism, subclinical hypothyroidism and hypothyroxinemia were0.60%,3.77%,6.49%,but there was no difference between the prevalences(P>0.05);(5)The ratio of higher urine iodine in subclinical hypothyroidism group at T3period was higher than that in normal thyroid function group(P<0.01),and the prevalence of overt hypothyroidism in higher urine iodine group was higher than that in normal urine iodine group(P<0.01);(6)There was a U-shaped curve between urine iodine level and the median of serum TSH,the prevalence of subclinical hypothyroidism and hypothyroxinemia;(7)The positive rate of TPOAb in the iodine deficient group of subclinical hypothyroidism was significantly higher than those with euthyroidism (P<0.01),and the prevalence of subclinical hypothyroidism in the TPOAb positive group was significantly higher than the TPOAb negative group(P<0.01);(8)There was no differences of the level of serum TSH,FT4between the higher age(>30years) and the lower age(≤30years)(P>0.05),and the prevalence of subclinical hypothyroidism,overt hypothyroidism, hypothyroxinemia between two groups was no differences (P>0.05).Conclusion:(1)There is no iodine deficiency among pregnant women groups in Qingdao, but still44.95%individuals expose in iodine insufficient.The ratio of iodine insufficient will increase with the extension of pregnancy;(2)The serum thyroid hormone levels present a series of dynamic change with increase in gestational weeks.Hypothyroidism during pregnancy performs mainly subclinical hypothyroidism and hypothyroxinemia;(3)There is a U-shaped curve between iodine intake and the prevalence of subclinical hypothyroidism at T1period, that is, iodine deficiency and iodine excess can lead to the prevalence of subclinical hypothyroidism increased;(4)Positive TPOAb is one of risk factors of subclinical hypothyroidism during pregnancy;(5)The gestational age may not be a risk factor for hypothyroidism during pregnancy.