An Inverse Relationship Between Iodine Intake and Thyroid Antibodies: A National Cross-Sectional Survey in Mainland China
THYROID
Authors: Teng, Di; Yang, Wenqing; Shi, Xiaoguang; Li, Yongze; Ba, Jianming; Chen, Bing; Du, Jianling; He, Lanjie; Lai, Xiaoyang; Li, Yanbo; Chi, Haiyi; Liao, Eryuan; Liu, Chao; Liu, Libin; Qin, Guijun; Qin, Yingfen; Quan, Huibiao; Shi, Bingyin; Sun, Hui; Tang, Xulei; Tong, Nanwei; Wang, Guixia; Zhang, Jin-an; Wang, Youmin; Xue, Yuanming; Yan, Li; Yang, Jing; Yang, Lihui; Yao, Yongli; Ye, Zhen; Zhang, Qiao; Zhang, Lihui; Zhu, Jun; Zhu, Mei; Shan, Zhongyan; Teng, Weiping
Abstract
Background:Iodine intake is associated with thyroid autoimmunity. In this study, we evaluated the changes in thyroid autoimmunity after 20 years of universal salt iodization (USI) in China. Methods:A total of 78,470 subjects (18 years or older) from 31 provincial regions of mainland China participated in the study. Serum thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), TSH receptor antibody, thyrotropin (TSH), and urinary iodine concentration (UIC) were measured. Results:Positive TPOAb and TgAb were detected in 10.19% [CI 9.80-10.59] and 9.70% [CI 9.28-10.13] of the subjects, respectively. The prevalence of positive isolated TPOAb (i-TPOAb), positive isolated TgAb (i-TgAb), and double positive TPOAb and TgAb (d-Ab) was 4.52%, 4.16%, and 5.94%, respectively. The prevalence of thyroid antibody positivity was the highest in the iodine-deficient (UIC <100 mu g/L) groups. The prevalence of i-TPOAb was inversely associated with more than adequate iodine intake (MAI) and excessive iodine intake (EI); the odds ratio (OR) was 0.89 [CI 0.81-0.98] for MAI and 0.90 [CI 0.81-0.99] for EI. We observed that i-TgAb, like i-TPOAb, was a high-risk factor for subnormal TSH levels (OR = 3.64 [CI 2.62-5.05]) and elevated TSH levels (OR = 1.62 [CI 1.49-1.77]). The prevalence of thyroid antibody positivity varied among five ethnic groups. Conclusions:After two decades of USI, the prevalence of thyroid antibody positivity has remained low. MAI and EI had an inverse relationship with TPOAb positivity, which reveals that UIC between 100 and 299 mu g/L is optimal and safe for thyroid autoimmunity. These conclusions need to be confirmed in a follow-up study because this study was a cross-sectional study.
The Joint Role of Iodine Status and Thyroid Function on Risk for Preeclampsia in Finnish Women: a Population-Based Nested Case-Control Study
BIOLOGICAL TRACE ELEMENT RESEARCH
Authors: Reische, Elijah C.; Mannisto, Tuija; Purdue-Smithe, Alexandra; Kannan, Kurunthachalam; Kim, Un-Jung; Suvanto, Eila; Surcel, Helja-Marja; Gissler, Mika; Mills, James L.
Abstract
Preeclampsia, a pregnancy disorder that includes hypertension and proteinuria, is a major cause of maternal and fetal morbidity and mortality. Some studies, but not all, have found that women with preeclampsia have significantly lower iodine levels than healthy pregnant women. Resolving this issue is important because iodine deficiency in pregnancy is common in the USA and parts of Europe including Finland. We conducted a nested case-control study to determine whether the risk for preeclampsia is associated with iodine status. We measured serum iodine, thyroglobulin (Tg), and thyroid stimulating hormone (TSH) at 10-14 weeks gestational age in 204 women with preeclampsia and 246 unaffected controls selected from all births in Finland. We found no significant difference in iodine (case mean = 26.04 ng/mL, control mean = 27.88 ng/mL,p= 0.995), Tg (case mean = 31.11 ng/mL, control mean = 29.61 ng/mL,p= 0.996), and TSH (case mean = 1.30 mIU/L, control mean = 1.24 mIU/L,p= 0.896) levels between cases and controls. There was no significant relationship between preeclampsia risk and iodine, Tg, or TSH after adjustment for known risk factors. These results are reassuring given the high prevalence of iodine deficiency in pregnancy.
COA
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