Associations of urinary iodine and blood selenium levels with subclinical hypothyroidism and thyroid antibodies during the first half pregnancy in Tianjin women

Abstract

Objective To investigate the associations of urinary iodine concentration(UIC)and blood selenium levels with subclinical hypothyroidism and thyroid antibodies during the first half pregnancy in women. Methods A total of 239 pregnant women(7-20 weeks)were selected. The baseline data were collected, and serum TSH, FT4, thyroid peroxidase antibody(TPOAb), thyroglobulin antibody(TgAb), blood selenium, and urinary iodine concentration(UIC)levels were measured. Results The median level of urinary iodine among 239 women was 156.96 μg/L. The distributions of pregnant women with iodine deficiency, iodine adequate, more-than-adequate or excessive iodine intake were 43.9%, 38.9%, 17.2%, respectively. The percentage of more-than-adequate and excessive iodine in women with subclinical hypothyroidism was higher than that in women with euthyroidism. The serum TSH level in women with UIC≥250 μg/L was higher than those with 150≤UIC<250 μg/L and UIC<150 μg/L(P<0.05). The serum TSH level in women with blood selenium<95 μg/L was higher than those with selenium≥95 μg/L(P<0.05). Logistic regression analysis showed that the risk of subclinical hypothyroidism in women with UIC≥250 μg/L was increased by 3.498 fold(95%CI 1.588-7.704)as compared with those with 150≤UIC<250 μg/L. The risk of subclinical hypothyroidism in women with blood selenium <80 μg/L was increased by 2.667 fold(95%CI 1.123-6.331)compared with those with 90≤selenium <100 μg/L. After adjusting for age, gestational weeks, residential district, TPOAb, TgAb, taking compound nutritional supplements, more-than-adequate and excessive iodine still increased the risk of subclinical hypothyroidism(OR=3.014, 95%CI 1.310-6.938). Women with UIC≥250 μg/L and blood selenium <95 μg/L revealed the increased risk of subclinical hypothyroidism as compared to those with 150≤UIC<250 μg/L and selenium≥95 μg/L(OR=5.429, 95%CI 1.929-15.281). After adjusting for age, gestational weeks, residential district, TPOAb, TgAb, taking compound nutritional supplements, the fingdings still existed. Conclusion The nutrient condition of iodine and selenium of the pregnant women in Tianjin during the first half pregnancy should be noticed. The individualized supplement of iodine and selenium, if needed, should be performed to decrease the risk of subclinical hypothyroidism. (Chin J Endocrinol Metab, 2018, 34: 38-43) Key words: The first half of pregnancy; Subclinical hypothyroidism; Thyroid antibodies; Urinary iodine; Blood selenium