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Iron deficiency increased hypothyroxinemia risk in pregnant, childbearing-aged women
Iron deficiency was linked to isolated hypothyroxinemia in pregnant women and women of childbearing age, according to research published in The Journal of Clinical Endocrinology & Metabolism.
The association was independent of the effects of both iodine and thyroid autoimmunity, suggesting iron deficiency could be a pathogenic factor for hypothyroxinemia, even during the first trimester, according to researchers.
“To our knowledge, the current study is the first population-based survey on association of iron deficiency with thyroid function during the first trimester of pregnancy in an iodine adequate area,” the researchers wrote.
Xiaohui Yu, PhD, of the department of endocrinology and metabolism, The First Hospital of China Medical University, Shenyang, and colleagues from other institutions examined relationships between iron deficiency and hypothyroid function in 7,953 pregnant women (≤12 weeks’ gestation) and 2,000 women of childbearing age.
The investigators also analyzed a subpopulation of 3,340 pregnant women and 1,052 women of childbearing age who had sufficient iodine intake and negative thyroid peroxidase antibody.
The researchers defined mild and severe hypothyroxinemia as free thyroxine levels below the 10th percentile and below the fifth percentile with normal thyroid-stimulating hormone. Total body iron, serum ferritin and serum transferrin receptor served as iron nutrition indicators.
Both pregnant and nonpregnant women with iron deficiency demonstrated lower serum free T4 levels (P<.05 for both) compared with the corresponding groups without iron deficiency. The prevalence of mild and severe hypothyroxinemia was noticeably higher in women with iron deficiency vs. those without, whether they were pregnant or not (P<.01 for all).
Based on logistic regression, iron deficiency was an independent risk factor for mild (OR=2.44; 95% CI, 1.32-4.49) and severe (OR=3.27; 95% CI, 1.44-7.44) hypothyroxinemia in pregnancy; the same was true for risk in nonpregnancy (OR=2.662; 95% CI, 1.33-5.329 for mild hypothyroxinemia, and OR=3.254; 95% CI, 1.375-7.7 for severe hypothyroxinemia).
“We speculate [iron deficiency] maybe a pathogenic factor for isolated hypothyroxinemia, even in women during the first trimester of pregnancy,” the researchers wrote. “However, further studies are needed to verify this.”
Disclosure: The researchers report no relevant financial disclosures.