Wenxing Guo1, Wei Wang2, Ya Jin1, Wen Chen1, Lu Chen3, Laixiang Lin4, Yuangui Cheng5, Tingkai Cui1, Yanting Chen1, Ziyun Pan1, Jun Shen6, Long Tan1, Min Gao1, Yixin Zhang1, Wanqi Zhang7,8,9. 1. The Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China. 2. The Department of Health Services and Management, School of Management, Tianjin University of Traditional Chinese Medicine, Tianjin, China. 3. Shandong Institute of Geophysical & Geochemical Exploration, Shandong, China. 4. Tianjin Institution of Endocrinology, Tianjin, China. 5. Gaoqing Center for Disease Control and Prevention, Shandong, China. 6. Department of Sanitary Chemistry, Tianjin Medical University, Tianjin, China. 7. The Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China, wqzhang@tmu.edu.cn. 8. Key Laboratory of Environment, Nutrition and Population Health of Tianjin, Tianjin, China, wqzhang@tmu.edu.cn. 9. Key Laboratory of Hormones and Development (Ministry of Health), Tianjin, China, wqzhang@tmu.edu.cn.
Abstract
OBJECTIVES: To explore trimester-specific thyroid function changes under different iodine statuses throughout pregnancy. METHODS: A cross-sectional study was conducted to assess the pregnancy iodine status, and 2,378 healthy pregnant women covering all 3 trimesters were recruited. Urinary iodine concentration (UIC) was measured by collecting spot urine samples. Blood samples were collected to evaluate thyroid function. Thyroid B-ultrasonography was conducted to measure the thyroid volume (Tvol). RESULTS: The median UIC was 168 μg/L (111-263 μg/L). The UIC, free triiodothyronine (FT3), and free thyroxine (FT4) were significantly decreased as the pregnancy progressed (p < 0.001, p for trend <0.001), while Tvol increased (p < 0.001, p for trend <0.001). Thyrotropin (TSH) was significantly different between the 3 trimesters and showed an upward trend (p < 0.001), but the p for trend was not significant (p for trend = 0.88). After stratification by UIC, there were no significant differences in serum TSH, FT4, or FT3 level between UIC groups. Tvol was significantly higher in the UIC ≥500 μg/L group in the first trimester (β: 2.41, 95% CI: 1.09-3.72, p <0.001), as well as in the 250 ≤ UIC < 500 μg/L group (β: 1.65, 95% CI: 0.61-2.70, p < 0.001) and UIC ≥500 μg/L group (β: 3.35, 95% CI: 1.96-4.74, p < 0.001) in the third trimester. CONCLUSIONS: No difference was observed in TSH, FT3, or FT4 among the different iodine status groups throughout pregnancy. Tvol increased as the pregnancy progressed, and it was especially higher in the UIC ≥500 μg/L group in the first and third trimesters.
OBJECTIVES: To explore trimester-specific thyroid function changes under different iodine statuses throughout pregnancy. METHODS: A cross-sectional study was conducted to assess the pregnancy iodine status, and 2,378 healthy pregnant women covering all 3 trimesters were recruited. Urinary iodine concentration (UIC) was measured by collecting spot urine samples. Blood samples were collected to evaluate thyroid function. Thyroid B-ultrasonography was conducted to measure the thyroid volume (Tvol). RESULTS: The median UIC was 168 μg/L (111-263 μg/L). The UIC, free triiodothyronine (FT3), and free thyroxine (FT4) were significantly decreased as the pregnancy progressed (p < 0.001, p for trend <0.001), while Tvol increased (p < 0.001, p for trend <0.001). Thyrotropin (TSH) was significantly different between the 3 trimesters and showed an upward trend (p < 0.001), but the p for trend was not significant (p for trend = 0.88). After stratification by UIC, there were no significant differences in serum TSH, FT4, or FT3 level between UIC groups. Tvol was significantly higher in the UIC ≥500 μg/L group in the first trimester (β: 2.41, 95% CI: 1.09-3.72, p <0.001), as well as in the 250 ≤ UIC < 500 μg/L group (β: 1.65, 95% CI: 0.61-2.70, p < 0.001) and UIC ≥500 μg/L group (β: 3.35, 95% CI: 1.96-4.74, p < 0.001) in the third trimester. CONCLUSIONS: No difference was observed in TSH, FT3, or FT4 among the different iodine status groups throughout pregnancy. Tvol increased as the pregnancy progressed, and it was especially higher in the UIC ≥500 μg/L group in the first and third trimesters.
Authors: Ye Bu; Yan Cai; Chunlei Ji; Chunyan Zhao; Chunyuan Tian; Bo Pang; Mengqi Shi; Xin Li; Ying Liu; Dianjun Sun Journal: Public Health Nutr Date: 2021-08-12 Impact factor: 4.022