Elevated first-trimester TSH may increase risk for gestational diabetes
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Key takeaways:
- Women with a higher TSH level in the first trimester of pregnancy have higher odds for gestational diabetes.
- The risk for gestational diabetes is higher for women with a BMI of 24 kg/m2 or more.
Women who have a higher thyroid-stimulating hormone level early in pregnancy may have an increased risk for developing gestational diabetes, according to findings published in The Journal of Clinical Endocrinology & Metabolism.
“Our findings indicate that elevated TSH in early pregnancy is a risk factor for gestational diabetes, even when the TSH level is within the normal range, providing new evidence that thyroid function during pregnancy affects gestational diabetes,” Chenghong Yin, MD, PhD, of the department of central laboratory at Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital in China, and colleagues wrote. “These results were further supported by the relatively high gestational diabetes rate in participants with subclinical hypothyroidism during pregnancy.”
Researchers conducted a prospective cohort study with 26,742 pregnant women who received regular prenatal care during their first trimester at Beijing Obstetrics and Gynecology Hospital from February 2018 to December 2021. Demographics and the presence of thyroid disease were obtained through an enrollment questionnaire. Blood samples were collected between 6 and 13 weeks of gestation to measure thyroid hormone levels. A 2-hour oral glucose tolerance test was conducted between 24 and 28 weeks gestation to determine whether participants had gestational diabetes.
Of the participants, 14.9% had gestational diabetes. Women with gestational diabetes had a higher TSH level (1.6 mIU/L vs. 1.52 mIU/L; P = .003), a lower free thyroxine level (16.27 pmol/L vs. 16.38 pmol/L; P = .007) and a higher thyroid peroxidase antibody positivity (12.5% vs. 11.3%; P = .037) than those without gestational diabetes. The proportion of women with subclinical hypothyroidism was similar between the two groups.
After adjusting for covariates, higher TSH (adjusted OR = 1.03; 95% CI, 1.007-1.054; P = .012) was associated with a greater likelihood for gestational diabetes. Women with subclinical hypothyroidism were more likely to develop gestational diabetes than those without subclinical hypothyroidism (aOR = 1.211; 95% CI, 1.01-1.451; P = .039). No associations between gestational diabetes and free T4 or thyroid peroxidase antibody positivity were observed.
When participants were divided into quintiles based on TSH and free T4 levels, women in the three highest quintiles for TSH were more likely to develop gestational diabetes than those in the lowest quintile. There was no difference in gestational diabetes odds between the free T4 groups.
In a subgroup analysis in which participants were separated by prepregnancy BMI, women with a BMI of 24 kg/m2 or higher who were in the highest TSH quintile had a higher risk for developing gestational diabetes compared with the lowest quintile. Odds for gestational diabetes were higher among women with a BMI of 24 kg/m2 or greater compared with women with a BMI of less than 24 kg/m2 within the same TSH quintile.
“Higher TSH levels may increase the risk of gestational diabetes, especially when prepregnancy BMI 24 kg/m2,” the researchers wrote. “However, because other possible confounders were not measured, the mechanisms remain unclear and require further investigation.”
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