Subclinical hypothyroidism in pregnant women with diabetes

Objective: To study whether a pregnant women is highly likely to develop subclinical hypothyroidism (SCH). Methods: In this cohort study, we recruited 62 pregnant women with diabetes mellitus (DM) (DM group) and 65 pregnant women without diabetes (control group). We divided our subjects with DM (n = 62) into two subgroups, as those with gestational DM (GDM, n = 28) and pregestational DM (pre-GDM, n = 34). From the time of the pregnant women's hospitalization, laboratory measurements of serum thyroid stimulating hormone (TSH), serum free thyroxine (FT4) were tested by electrochemiluminescence immunoassay. Between 24 and 28 weeks of gestation, blood glucose (BG) was measured by the hexokinase method, glycosylated hemoglobin (HbA1c) by HLC-723G7, and high/low density lipoprotein cholesterol (H/LDL-C) were performed by the enzyme colorimetry. Results: The prevalence of SCH in the GDM group did not differ significantly from that in the control group (P = 0.13), but differences existed between the pre-GDM and control groups (P < 0.01). BMI, systolic and diastolic blood pressure, FPG, HbA1c, BUN, total cholesterol level, and triglyceride values were higher in pregnant women of the pre-GDM group and GDM group than those of the control group. The pregnant women with SCH tended to have poorer blood glucose control and higher body mass index (BMI). The findings indicated that poor blood glucose control and higher BMI increased the possibility of occurrence of SCH in pregnant women with diabetes. Conclusion: SCH should be considered for pregnant women exhibiting weak glycemic control and obesity.