The relationship between iron level and thyroid function during the first trimester of pregnancy: A cross-sectional study in Wuxi, China

Fu, Junfen; Yang, Anqiang; Zhao, Jun; Zhu, Yu‐Cheng; Gu, Ying; Xu, Yaohui; Chen, Daozhen

doi:10.1016/j.jtemb.2017.01.004

Cited by 15 publications

(17 citation statements)

References 30 publications

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“…In their meta-analysis, Talebi et al, observed decreased iron levels in patients with subclinical hypothyroidism [ 216 ]. Consistent with this finding, another study conducted on 1764 pregnant women showed an increase in TSH levels and a decrease in fT4 levels in the iron deficiency group [ 225 ]. Although few, studies in euthyroid individuals mainly observed a decrease in thyroid hormone levels [ 226 , 227 , 228 ] and no change in TSH levels [ 226 , 227 , 228 ] in patients with anemia or iron deficiency ( Table 1 ).…”

Section: Environmental Factors That Influence Tsh and Thyroid Hormone Levelssupporting

confidence: 71%

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Leko

Gunjača

Pleić

et al. 2021

IJMS

118

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Thyroid hormones are necessary for the normal functioning of physiological systems. Therefore, knowledge of any factor (whether genetic, environmental or intrinsic) that alters the levels of thyroid-stimulating hormone (TSH) and thyroid hormones is crucial. Genetic factors contribute up to 65% of interindividual variations in TSH and thyroid hormone levels, but many environmental factors can also affect thyroid function. This review discusses studies that have analyzed the impact of environmental factors on TSH and thyroid hormone levels in healthy adults. We included lifestyle factors (smoking, alcohol consumption, diet and exercise) and pollutants (chemicals and heavy metals). Many inconsistencies in the results have been observed between studies, making it difficult to draw a general conclusion about how a particular environmental factor influences TSH and thyroid hormone levels. However, lifestyle factors that showed the clearest association with TSH and thyroid hormones were smoking, body mass index (BMI) and iodine (micronutrient taken from the diet). Smoking mainly led to a decrease in TSH levels and an increase in triiodothyronine (T3) and thyroxine (T4) levels, while BMI levels were positively correlated with TSH and free T3 levels. Excess iodine led to an increase in TSH levels and a decrease in thyroid hormone levels. Among the pollutants analyzed, most studies observed a decrease in thyroid hormone levels after exposure to perchlorate. Future studies should continue to analyze the impact of environmental factors on thyroid function as they could contribute to understanding the complex background of gene–environment interactions underlying the pathology of thyroid diseases.

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Section: Environmental Factors That Influence Tsh and Thyroid Hormone Levelssupporting

confidence: 71%

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Leko

Gunjača

Pleić

et al. 2021

IJMS

118

View full text Add to dashboard Cite

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“…ID is frequent during the first trimester of pregnancy and is often related to a higher prevalence of thyroid autoimmunity, increased TSH, and lower FT3 levels ( 27 ). A study in Wuxi also confirmed that low iron stores showed a trend toward higher TSH, lower FT3, and lower FT4 levels during the first trimester of pregnancy ( 15 ). A study in Suzhou revealed that pregnant women with mild ID and ID anemia have higher TSH and lower FT4 status ( 16 ).…”

Section: Discussionmentioning

confidence: 72%

Mild Anemia May Affect Thyroid Function in Pregnant Chinese Women During the First Trimester

et al. 2021

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BackgroundPregnant women are often susceptible to anemia, which can damage the thyroid gland. However, compared with moderate and severe anemia, less attention has been paid to mild anemia. The purpose of this study was to evaluate the effect of mild anemia on the thyroid function in pregnant women during the first trimester.MethodsA total of 1,761 women in the first trimester of their pregnancy were enrolled from Shenyang, China, and divided into mild anemia and normal control groups based on their hemoglobin levels. Thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) levels were compared between the two groups.ResultsThe TSH levels of pregnant women with mild anemia were higher than those of pregnant women without mild anemia (p < 0.05). Normal control women were selected to set new reference intervals for TSH, FT3, and FT4 levels during the first trimester, which were 0.11–4.13 mIU/l, 3.45–5.47 pmol/l, and 7.96–16.54 pmol/l, respectively. The upper limit of TSH 4.13 mU/l is close to the upper limit 4.0 mU/l recommended in the 2017 American Thyroid Association (ATA) guidelines, indicating that exclusion of mild anemia may reduce the difference in reference values from different regions. Mild anemia was related to 4.40 times odds of abnormally TSH levels (95% CI: 2.84, 6.76) and 5.87 increased odds of abnormal FT3 (95% CI: 3.89, 8.85). The proportion of hypothyroidism and subclinical hypothyroidism in patients with mild anemia was higher than that in those without anemia (0.6% vs. 0, p = 0.009; 12.1% vs. 1.9%, p < 0.001). Mild anemia was related to 7.61 times increased odds of subclinical hypothyroidism (95% CI: 4.53, 12.90).ConclusionsMild anemia may affect thyroid function during the first trimester, which highlights the importance of excluding mild anemia confounding when establishing a locally derived specific reference interval for early pregnancy.

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“…However, no meta-analysis had been conducted to investigate the effect of maternal thyroid dysfunction on anemia. A cross-sectional study in China indicated that pregnancies with IDA show lower FT4 levels compared with the control group during the first trimester of pregnancy (37). Another article showed that Hb correlated positively with FT4 and FT3 and negatively with TSH (5).…”

Section: Discussionmentioning

confidence: 99%

Maternal Thyroid Dysfunction and Gestational Anemia Risk: Meta-Analysis and New Data

et al. 2020

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Background: Previous studies indicate the effects of thyroid dysfunction on adverse obstetric outcomes and fetal neurodevelopment, of which the results on gestational anemia are controversial. Here, we evaluated the influence of thyroid dysfunction on gestational anemia via published epidemiological articles and a new prospective study conducted by our team, respectively. Methods: We searched studies on the PubMed, Embase, MEDLINE, and Cochrane databases as of November 2019, and conducted a prospective study in which participants underwent thyroid function and blood routine testing throughout pregnancy. Results: The meta-analysis showed that pregnancies with overt hypothyroidism [OH; odds ratio (OR) = 3.74, 95% confidence interval (CI): 1.95-7.15] or that were thyroid peroxidase antibody (TPOAb)-positive (OR = 1.97, 95%CI: 1.19-3.26) had increased anemia risk, but similar results were not found in pregnancies with subclinical hypothyroidism (SCH) and hyperthyroidism. In the prospective study from our new data, the hypothyroid group had significant reductions in hemoglobin (Hb) (P = 0.048) and increased anemia risk (OR = 6.384, 95%CI: 2.498-16.311) during the second half of pregnancy. From the first to second half of pregnancy, the longitudinal reductions in Hb, erythrocyte (RBC), and hematocrit (Hct) levels were significantly increased in hypothyroid group. Conclusions: Our meta-analysis indicates that untreated OH or TPOAb-positive pregnant women have increased risk of anemia. In addition, our new data showed that treated hypothyroidism is also a risk factor for anemia in the second half of pregnancy rather than in the first half. The results may guide strengthening of Hb monitoring in pregnancies with thyroid dysfunction.

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The relationship between iron level and thyroid function during the first trimester of pregnancy: A cross-sectional study in Wuxi, China

Cited by 15 publications

References 30 publications

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Environmental Factors Affecting Thyroid-Stimulating Hormone and Thyroid Hormone Levels

Mild Anemia May Affect Thyroid Function in Pregnant Chinese Women During the First Trimester

Maternal Thyroid Dysfunction and Gestational Anemia Risk: Meta-Analysis and New Data

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