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Thyroid function in early pregnancy may predict gestational diabetes risk
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Among pregnant women, a thyroid hormone marker indicating the conversion rate from thyroxine to triiodothyronine measured during the first and second trimesters may serve as an independent predictor of gestational diabetes risk, according to findings from a case-control study published in The Journal of Clinical Endocrinology & Metabolism.
“Screening for thyroid dysfunction during pregnancy is still controversial, even though, among nonpregnant individuals, it can lead to earlier detection and treatment of metabolic diseases,” Cuilin Zhang, MD, PhD, of the National Institute of Child Health and Human Development in Rockville, Maryland, said in a press release. “Our study found that women with thyroid abnormalities in the first half of pregnancy are at an increased risk for gestational diabetes, a common pregnancy complication that can cause short- and long-term health problems for women and their children.”
Zhang and colleagues analyzed medical records data from 107 women with gestational diabetes and 214 pregnant women without gestational diabetes (matched controls) from the Fetal Growth Studies-Singleton Cohort, a multiracial pregnancy cohort of 2,802 women conducted between 2009 and 2013 at 12 U.S. clinical centers. Researchers assessed blood samples collected from women at four points during pregnancy (including first and second trimester) to measure concentrations of thyroid-stimulating hormone, free T3, free T4, thyroglobulin antibody and thyroid peroxidase antibody, as well as the ratio of free T3 to free T4. Researchers used conditional logistic regression analysis to estimate trimester-specific associations between thyroid markers and subsequent gestational diabetes risk, adjusting for thyroid autoimmunity status and gestational diabetes risk factors.
The researchers found that free T3 concentration and free T3 to free T4 ratio were positively associated with development of gestational diabetes.
Women in the highest quartile of free T3 concentration during their first trimester were four times more likely to develop gestational diabetes vs. women in the lowest quartile (adjusted OR = 4.25; 95% CI, 1.67-10.8), with the odds for gestational diabetes falling slightly for women in the highest free T3 quartile vs. the lowest quartile during their second trimester (aOR = 3.89; 95% CI, 1.5-10.1).
Similarly, pregnant women in the highest quartile of free T3 to free T4 ratio in the first trimester were nearly nine times more likely to develop gestational diabetes vs. women in the lowest quartile (aOR = 8.63; 95% CI, 2.87-26), whereas women in the highest free T3 to free T4 ratio during the second trimester were nearly 14 times more likely to develop gestational diabetes (aOR = 13.6; 95% CI, 3.97-46.3).
Results persisted in sensitivity analyses excluding pregnant women with elevated thyroid antibodies, prior history of gestational diabetes or preeclampsia, or who smoked before pregnancy.
Researchers observed no associations between TSH or free T4 and development of gestational diabetes. However, the researchers noted an association between hypothyroxinemia during pregnancy and gestational diabetes. Compared with euthyroid pregnant women, women with hypothyroxinemia during their second trimester were nearly three times more likely to develop gestational diabetes (aOR = 2.97; 95% CI, 1.07-8.24).
“These findings, in combination with previous evidence of thyroid-related adverse pregnancy outcomes, support the benefits of thyroid screening among pregnant women in early to mid-pregnancy,” Zhang said in the release. – by Regina Schaffer
Disclosures: The authors report no relevant financial disclosures.
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