Endocrine Abstracts

Introduction: Gestational diabetes (GD) is one of the most common complications of pregnancy. Thyroid hormones play an important role in carbohydrate homeostasis, however, their influence on the risk of developing gestational diabetes has shown contradictory results.

Objective: To explore whether variations in thyroid function parameters, within the thresholds of normality, can be associated with the risk of developing GD.

Material and Methods: In a case-control study, 107 pregnant women (37 cases and 70 controls) matched according to age, BMI and previous pregnancies, from a sufficient iodine population and with normal thyroid function were included. TSH, fT4 and fT3 and the fT3/fT4 ratio were assessed in the first (week 10–12) and second (week 24–28) trimester of pregnancy. Biomarker levels were categorized into tertiles and the odds ratio (OR) for gestational diabetes was calculated as a measure of association with their 95% CI.

Results: Mean age was 33.24 ± 5.1 years in cases and 32.97 ± 4.5 years in controls (P = 0.779). There were also no significant differences between the groups in their BMI, smoking habits, presence of antithyroid antibodies, use of iodized salt or iodized supplements. Of the parameters analyzed, only the fT3: 3.10 ± 0.27 vs 2.86 ± 0.25 (P < 0.05) and the fT3/fT4 ratio: 2.94 ± 0.35 vs 2.67 ± 0.29 (P < 0.05) in the first trimester showed significantly different values between cases and controls. Patients with fT3 and fT3/fT4 levels in the higher tertile presented a higher risk of GD than pregnant women in the lower tertile. The association was: OR 7.50 (2.47–22.69) and OR 4.38 (1.51–12.64) for fT3 and fT3/fT4 ratio respectively. No significant associations were identified in any of the other parameters analyzed.

Conclusions: Our results suggest that pregnant women with the highest levels of fT3 and fT3/fT4 in the first trimester of pregnancy are at increased risk of developing gestational diabetes regardless of traditional risk factors.