Abstract
BackgroundIron 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.MethodsIn 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).ResultsFor 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.ConclusionsID 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.
Highlights
Thyroid dysfunction is a common endocrine disorder in pregnant women, and consists of imbalanced thyroid hormone levels and positive thyroid antibody status
A systematic review and meta-analysis was conducted to answer the following PICO question: “Do pregnant or reproductive-age women with Iron deficiency (ID) have a higher risk of thyroid function or autoimmune abnormalities than them without ID?” The Preferred Reporting Items for systematic review and metaanalysis protocols (PRISMA-P) were referenced in the process of carrying out our meta-analyses [16]
A total of 636 articles were searched from the Cochrane, Embase, Medline and PubMed databases based on the keywords
Summary
Thyroid dysfunction is a common endocrine disorder in pregnant women, and consists of imbalanced thyroid hormone levels (including overt and subclinical hypothyroidism, overt and subclinical hyperthyroidism) and positive thyroid antibody status. Studies have shown that about 0.3%–3% of pregnant women suffer from hypothyroidism [1]. Hypothyroidism leads to multiple adverse outcomes such as premature delivery, miscarriage, neurodevelopmental dysplasia, and increased risk of autism and asthma in the offspring [1,2,3,4,5]. More pregnant women (about 18%) are tested positive for thyroid autoantibodies (Thyroid peroxidase antibody, TPOAb or thyroglobulin antibody, TgAb), which will adversely affect pregnant women and their offspring [1]. Pregnant women with positive thyroid antibodies have a higher risk of preterm birth and their infants are more likely to suffer from respiratory distress [7]. The aim of the current study was to summarize the evidences and evaluate the relationship between ID and thyroid disorders
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