Introduction: Hypothyroidism and subclinical hypothyroidism may be associated with hypertension and metabolic syndrome. The aim of this study was to investigate the relationship between thyroid-stimulating hormone (TSH) and blood pressure, as well as the relationship between thyroid function and insulin resistance in middle-aged and elderly Chinese.
Methods: This was a cross-sectional, community-based study. Serum TSH, fasting glucose and insulin were measured in 2,988 subjects aged 35-80 years. Logistic regression analysis was used to identify the risk factors for hypertension. Analysis of variance and multiple linear regression analysis were performed to characterise the relationship among TSH, insulin resistance and blood pressure.
Results: Higher serum TSH concentration was found to be an independent risk factor for hypertension in females (odds ratio 1.4, 95% confidence interval 1.02-1.93; p-value = 0.039). The female group with subclinical hypothyroidism and high normal TSH (2.5-4.8 mIU/L) were more susceptible to high blood pressure than those with low normal TSH (0.3-2.5 mIU/L) (p-value < 0.05). After adjustment for waist-hip ratio and body mass index, neither the correlation between blood pressure and homeostasis model assessment of insulin resistance (HOMA-IR) nor the correlation between TSH and HOMA-IR were found to be significant in this study.
Conclusion: This study provides evidence that both subclinical hypothyroidism and high normal TSH are independent risk factors for hypertension in middle-aged and elderly Chinese women.