Endocrine Abstracts

Introduction

Gestational diabetes mellitus (GDM) may frequently be overcome by nutrition therapy alone, but insulin regimen may be necessary in about 30 % of the patients with GDM. It was known that thyroid hormones were associated with glucose metabolism. Therefore, we aimed to investigate the association of fT4 level with insulin requirement in euthyroid pregnant women with GDM.

Materials and methods

We consecutively included euthyroid patients with GDM, and excluded those with thyroid dysfunction or any previous history of use of levothyroxine or antithyroid drug. The diagnosis of GDM was based on ADA criteria. Demographic features, previous history of GDM, gestational hypertension, insulin requirement (absent vs present or basal vs intensive regimen) and dose, nutrition and exercise adherence, and HbA1c, TSH, fT4, fT3, 25(OH) vitamin D3 levels were analyzed. We grouped the patients according to fT4 levels: lower than mid-normal (group A) vs upper than mid-normal (group B), or lower than normal range vs in normal range. We assessed the patients in 3rd trimester after 34th weeks of the pregnancy.

Results

Of total (n = 228), insulin was necessary in 58 patients. Insulin use was more frequent in the patients with fT4 level lower than normal range than those with normal fT4 (P = 0.003, OR:5.69 (95% CI 1.60–20.24)). Number of insulin injections was higher in group A than group B (0.022). fT4 level was not associated with insulin dose, HbA1c level, previous history of GDM, or diet adherence.

Conclusion

Lower fT4 level even in normal range may worsely affect glucose metabolism in euthyroid pregnant women with GDM. Our findings suggest that euthyroid hypothyroxinemia in pregnancy may be associated with difficulty in control of hyperglycemia. GDM would be an indication for treatment with levothyroxine in euthyroid hypothyroxinemia.