Dr. Michael Boah

Background Pregnant women are among the key groups in iodine nutrition evaluation. The purpose of the present study was to summarize the evidence supporting the relationship between mild iodine deficiency (UIC: 100–150 μg/L) in pregnant women and levels of thyroid function tests. Methods This review follows the guidelines for systematic reviews (PRISMA 2020). Three electronic databases (PubMed, Medline, and Embase) were searched for relevant publications in English on the association between mild iodine deficiency in pregnant women and thyroid function. Articles published in Chinese were searched in China’s electronic databases (CNKI, WanFang, CBM, and WeiPu). Pooled effects were presented as standardized mean differences (SMDs) and odds ratios (ORs) with 95% confidence intervals (CIs) using fixed or random effect models, respectively. This meta-analysis was registered at www.crd.york.ac.uk/prospero as CRD42019128120. Results We summarized the results from 7 articles with 8261 participants. The overall pooled results showed that the levels of FT3, FT4, and abnormal TgAb (the antibody levels exceeded the upper limit of the reference range) were significantly increased in pregnant women with mild iodine deficiency compared to pregnant women with adequate iodine status (FT3: SMD=0.854, 95% CI: 0.188, 1.520; FT4: SMD=0.550, 95% CI: 0.050, 1.051; TgAb: OR=1.292, 95% CI: 1.095; 1.524). Subgroup analysis was carried out on the sample size, ethnicity, country, and gestation of FT3, FT4, and TSH, but no plausible factor was found. Egger’s tests indicated no publication bias.The increase in FT3 and FT4, as well as TgAb levels, in pregnant women is associated with mild iodine deficiency. Conclusion Mild iodine deficiency is associated with an increase in FT3，FT4 and TgAb levels in pregnant women. Mild iodine deficiency may increase the risk of thyroid dysfunction in pregnant women.

To comprehensively evaluate the relationship between high iodine concentration and biomarker abnormalities related to autoimmune thyroiditis in a Chinese population. Medline, PubMed, and Embase electronic databases were searched for articles published domes- tically and internationally on the relationship between high iodine concentrations and thyroid hormone antibodies and thyroid- stimulating hormone in China before March 2019. Articles published in Chinese were searched in the China Biology Medicine (CBM) disc, Wanfang Database, and China National Knowledge Infrastructure (CNKI). A total of 16 cross-sectional articles were included in this study, including 9061 participants. A meta-analysis was conducted in Stata 14.0. The binary categorical and continuous variables used odds ratios (ORs) and standardized mean differences (SMDs) with the corresponding 95% confidence intervals (CIs) as the effect statistics, respectively. The results showed that high iodine concentrations had a minimal association with the abnormal rates of thyroid peroxidase antibody (TPOAb) (OR = 1.274, 95% CI (0.957, 1.695), P > 0.05) and thyroglobulin antibody (TGAb) (OR = 1.217, 95% CI (0.911, 1.626), P > 0.05) in the entire population. The thyroid-stimulating hormone (TSH) level in the high iodine group was greater than that in the adaptive iodine group (SMD = 0.202, 95% CI (0.096, 0.309), P < 0.05). The results of the subgroup analysis showed that the abnormal TPOAb rate in pregnant women (OR = 1.519, 95% CI (1.007, 2.291), P < 0.05) and children (OR = 3.365, 95% CI (1.966, 5.672), P < 0.05) in the high iodine group was greater than that in the adaptive iodine group, and the abnormal TGAb rate of children in the high iodine group was greater than that in the adaptive iodine group. The TSH levels of lactating women (SMD = 0.24, 95% CI (0.053, 0.427), P < 0.05), pregnant women (SMD = 0.301, 95% CI (0.176, 0.426), P < 0.05), and children (SMD = 0.25, 95% CI(0.096, 0.309), P < 0.05) in the high iodine group were higher than those in the adaptive iodine group. Egger’s and Begg’s tests showed no significant (P > 0.1) publication bias. High iodine can increase the risk of abnormal levels of TPOAb, TGAb, and TSH related to autoimmune thyroiditis in pregnant women, lactating women, and children in China.