Women in early pregnancy who have high levels of the thyroid hormone triiodothyronine (T3) may be more than four times more likely to develop gestational diabetes, compared to women who have normal levels of the hormone, according to researchers at the National Institutes of Health.
The thyroid hormone triiodothyronine T3 is produced from the related hormone thyroxine (T4).
The researchers also found that a high T3/T4 ratio — which indicates a high conversion rate from T4 to T3 — was strongly associated with a higher risk for gestational diabetes.
Triiodothyronine (T3) is the biologically-active thyroid hormone involved in glucose metabolism.
fT3:fT4 ratio, a marker indicating conversion of free thyroxine (fT4) to free T3 (fT3), is also implicated in glucose homeostasis.
To conduct the study, researchers evaluated medical records of 107 women with gestational diabetes, comparing them to 214 pregnant women who had not developed the condition.
The women had taken part in the NICHD Fetal Growth Study, a diverse sample of more than 2,300 participants.
Thyroid markers (fT3, fT4, TSH) were measured and fT3:fT4 ratio was derived across four visits in pregnancy, including first (gestational weeks 10-14) and second (weeks 15-26) trimester.
Conditional logistic regression adjusting for thyroid autoimmunity status and major gestational diabetes risk factors estimated trimester-specific associations of thyroid markers with subsequent gestational diabetes risk.
The authors note that abnormal thyroid functioning has been linked to miscarriage and preterm birth.
Their findings suggest that screening pregnant women for thyroid disease early in pregnancy could help identify women at high risk for gestational diabetes and other pregnancy-related complications.
For more information
Journal of Clinical Endocrinology and Metabolism
A longitudinal study of thyroid markers across pregnancy and the risk of gestational diabetes
U.S. National Institutes of Health
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