One of the parts of the thyroid jigsaw that is most often repeated here is the importance of iron levels. Here, in the context of pregnancy, another paper highlighting the importance of adequate iron. Yet, most of the time, we hear of standard treatment being ferrous sulphate - and the difficulty people have in taking it.
Thyroid. 2018 Jul 3. doi: 10.1089/thy.2017.0491. [Epub ahead of print]
Iron Deficiency May Predict Greater Risk for Hypothyroxinemia: A Retrospective Cohort Study of Pregnant Women in China.
Teng X1, Shan Z2, Li C3, Yu X4, Mao J5, Wang W6, Xie X7, Du J8, Zhang S9, Gao Z10, Zhang X11, Li L12, Fan C13, Teng W14.
Author information
Abstract
Background
Pregnant women are highly vulnerable to iron deficiency (ID) due to the increased iron needs during pregnancy. ID decreases circulating thyroid hormone concentrations likely through impairment of iron-dependent thyroid peroxidase (TPO). The present study aimed at exploring the association between ID and hypothyroxinemia in a retrospective cohort of pregnant women in China.
Methods
To investigate the relationship between ID and hypothyroxinemia, we retrospectively analyzed 723 pregnant women in the present study, including 675 and 309 women in the second trimester and third trimester, respectively. The trimester-specific hypothyroxinemia was defined as free thyroxine (FT4) levels below the 2.5th percentile of the reference range with serum thyrotropin (TSH) levels in the normal or higher than the 97.5th percentile of reference range in each trimester of pregnancy. Serum TSH, FT4, thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TgAb), serum ferritin (SF), soluble transferrin receptor (sTfR), and urinary iodine concentrations (UIC) were measured. SF, sTfR, and total body iron (TBI) were used to indicate the nutritional iron status.
Results
Cross-sectional multiple linear regression analysis showed that iron status was positively associated with serum FT4 levels in the first and second trimesters of pregnancy, but not in the third trimester. Logistic regression analysis showed that ID was an independent risk factor for hypothyroxinemia (odds ratio [OR] = 14.86, 95% confidence interval [95% CI] = 2.31-95.81, p = 0.005 in the first trimester and OR = 3.36, 95% CI = 1.01-11.21, p = 0.048 in the second trimester). The prospective analysis showed that pregnant women with ID during the first trimester of pregnancy had lower serum FT4 levels and a higher rate of hypothyroxinemia in the second or third trimester than those without ID.
Conclusions
ID appears to be a risk factor to predict hypothyroxinemia in the first and second trimesters of pregnancy, but not in the third trimester. We suggest that pregnant women with ID in the first and second trimesters be regarded as a high-risk group for maternal hypothyroxinemia.
PMID: 29968513
DOI: 10.1089/thy.2017.0491
