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Meta-Analysis
. 2021 Feb 25:12:629831.
doi: 10.3389/fendo.2021.629831. eCollection 2021.

Iron Deficiency, a Risk Factor of Thyroid Disorders in Reproductive-Age and Pregnant Women: A Systematic Review and Meta-Analysis

Jingyi Luo  1 , Xiaoxia Wang  1 , Li Yuan  2 , Lixin Guo  1
Affiliations
Meta-Analysis

Iron Deficiency, a Risk Factor of Thyroid Disorders in Reproductive-Age and Pregnant Women: A Systematic Review and Meta-Analysis

Jingyi Luo et al. Front Endocrinol (Lausanne). .

Abstract

Background: Iron deficiency (ID) is concerned as the most common nutritional deficiency worldwide. The effects of ID on thyroid function and autoimmunity in pregnant women and reproductive-age women are controversial. The aim of the current study was to summarize the evidences and evaluate the relationship between ID and thyroid disorders.

Methods: In this systematic review and meta-analysis, studies published on the Cochrane, Embase, Medline, and PubMed databases by October 2020 were searched. A total of 636 studies which discussed the correlation between ID and thyroid disorders were eligible in the initial search. Pooled mean differences (MD) and 95% confidence intervals (CI) were calculated for the assessment of thyrotropin (TSH) and free thyroxine (FT4) levels. Combined odd ratios (OR) and 95% CI were calculated for the assessment of the prevalence of overt and subclinical hypothyroidism, positive thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb).

Results: For women of reproductive age, ID could significantly increase the risk of positive TPOAb (OR: 1.89; 95% CI: 1.17, 3.06: P = 0.01) and both positive TPOAb and TgAb (OR: 1.48; 95% CI: 1.03, 2.11: P = 0.03). The meta-analysis of pregnant women showed that pregnant women with ID had increased serum TSH levels (MD: 0.12; 95% CI: 0.07, 0.17; P < 0.00001) and decreased FT4 levels (MD: -0.73; 95% CI: -1.04, -0.41; P < 0.00001). Meanwhile, the prevalence of overt (OR: 1.60; 95% CI: 1.17, 2.19; P = 0.004) and subclinical (OR: 1.37; 95% CI: 1.13, 1.66; P = 0.001) hypothyroidism in pregnant women with ID was significantly increased.

Conclusions: ID may adversely affect thyroid function and autoimmunity of pregnant and reproductive-age women and it is very necessary for monitoring iron nutritional status and early treatment of ID for them.

Keywords: iron deficiency; pregnant; reproductive-age; thyroid autoantibody; thyroid function.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Flow chart of the study selection process.
Figure 2
Figure 2
Forest plot of studies comparing reproductive-age women with iron deficiency (ID) to them without iron deficiency (Control) for (A) TSH, (B) FT4 and prevalence of (C) positive TPOAb, (D) positive TgAb, and (E) positive TPOAb and TgAb.
Figure 3
Figure 3
Forest plot of studies comparing pregnant women with iron deficiency (ID) to them without iron deficiency (Control) for (A) TSH, (B) FT4, and prevalence of (C) overt hypothyroidism, (D) subclinical hypothyroidism, (E) positive TPOAb, (F) positive TgAb, and (G) positive TPOAb and TgAb.
Figure 4
Figure 4
Forest plot of the subgroup analysis showing the comparison of prevalence of positive TPOAb in pregnant women with iron deficiency (ID) to those without iron deficiency (Control) according to different diagnostic crriteria for ID. Subgroup 1: <15ng/dl; Subgroup 2: <20ng/dl.
See this image and copyright information in PMC

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