Introduction: The aim of this study was to investigate insulin resistance in patients with mild and severe subclinical hypothyroidism (SH), and to explore the relationship between insulin resistance and cardiovascular risk factors.
Material and Methods: The study group consisted of 27 women with severe SH (body mass index [BMI], 28.35/3.92 kg/m2), 25 women with mild SH (BMI, 27.13/3.16 kg/m2), and 22 healthy women (BMI, 27.365/2.92 kg/m2). The mean systolic blood pressure, diastolic blood pressure, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), total cholesterol, LDL-cholesterol (LDL-C), triglyceride, thyroid-stimulating hormone (TSH), and high-sensitive CRP (hs-CRP) levels were higher in patients with severe SH than patients with mild SH and control subjects. The mean fasting insulin level, TSH level, LDL-C, and hs-CRP was higher in patients with mild SH than the control group. However, systolic blood pressure, diastolic blood pressure, and HOMA-IR were similar between patients with mild SH and those in the control group. In patients with severe SH, HOMA-IR was positively associated with TSH, total cholesterol, LDL-C, triglyceride, hs-CRP, and diastolic blood pressure but negatively associated with HDL-C. There was no correlation between HOMA-IR and waist circumference, W/H ratio, fT3, fT4, and systolic blood pressure in patients with severe SH. In patients with mild SH, HOMA-IR was positively correlated with TSH and hs-CRP, but there was no correlation between HOMA-IR and other parameters.
Conclusion: We conclude that severe SH was associated with increased insulin resistance and increased cardiovascular risk factors such as lipid abnormalities, hypertension, and hs-CRP. Our data also suggest that insulin resistance may play a role in mediating the effects of severe SH on diastolic blood pressure, lipid abnormalities, and low-grade inflammation. Mild SH is associated only with early insulin resistance, LDL-C, and low-grade inflammation.