Frequency of isolated maternal hypothyroxinemia in women with gestational diabetes mellitus in a moderately iodine-deficient area

Abstract

Aim: To investigate frequency of isolated maternal hypothyroxinemia (IMH) in women with gestational diabetes mellitus (GDM) using both the method specific trimester range (MSTR) and the standard reference range (SRR).

Methods: Our study included 50 GDM patients (case group) and 60 non-GDM pregnant (control group). Glucose, insulin, HOMA-IR, fT4 and TSH values were measured when pregnancy was confirmed in all participants. Thyroid function tests were measured in each trimester using the SRR and the MSTR.

Results: In the second and third trimesters, mean fT4 levels were significantly lower in the case group compared to the control group, based on the SRR (p < 0.001). Mean fT4 levels were within the normal reference range in both groups, based on the MSTR; however, the levels were significantly lower in the case group (p < 0.001). Using the SRR, IMH frequencies in the second and third trimesters, in the case group were 56 and 86%, respectively, and were 13.3 and 46.7%, respectively, in the control group (p < 0.001). Using the MSTR, the IMH frequencies in the second and third trimesters were 8 and 14%, respectively; there were no instances of IMH in the control group.

Conclusion: This study shows that changes in glucose metabolism may affect the thyroid hormone levels (fT4). Additionally, evaluating thyroid function tests in GDM patients using the MSTR can give more accurate results.

Chinese abstract

目的：应用正常孕妇早中晚孕期甲状腺激素参考值范围(MSTR)和标准参考值范围(SRR)两种标准研究妊娠期糖尿病（GDM）妇女中单纯性低甲状腺素血症（IMH）的发生率。

方法：本研究包括50名GDM患者（病例组）和60名非GDM的孕妇（对照组）。所有参与者一旦确认怀孕均要测定葡萄糖、胰岛素、稳态模型评估的胰岛素抵抗指数（HOMA-IR）、游离T4（fT4）和促甲状腺激素（TSH）水平。妊娠早中晚期均测定甲状腺功能，并应用SRR和MSTR两种标准进行评估。

结果：在孕中期和孕晚期，应用SRR标准评估，病例组平均fT4水平明显低于对照组(p<0.001)，基于MSTR标准，两组平均fT4水平均在正常参考范围内；然而，病例组水平明显低于对照组(p<0.001)。应用SRR标准，病例组孕中期和孕晚期IMH发生率分别为56%和86%，对照组分别为13.3 %and 46.7% (p<0.001)。应用MSTR标准，病例组孕中期和孕晚期IMH发生率分别为8%和14%，对照组则没有IMH病例。

结论：这项研究表明葡萄糖代谢的变化会影响甲状腺激素（fT4）的水平。另外，用MSTR标准评价GDM患者甲状腺功能可以得到更加准确的结果。

• Gestational diabetes mellitus
• isolated maternal hypothyroxinemia
• thyroid peroxidase antibody

Declaration of interest

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

The authors have no direct or indirect commercial, financial incentive associated with publishing this article.