A cross-sectional survey of relationship between serum TSH level and blood pressure

It is still controversial whether subclinical hypothyroidism and euthyroidism affect blood pressure. The study aimed to explore the relationship between different levels of thyroid-stimulating hormone (TSH) and blood pressure in the participants with subclinical hypothyroidism and euthyroidism. A total of 1319 participants were administered a questionnaire survey, and their blood pressure, height and body weight measurements were taken. Blood samples were taken to test serum TSH. FT3 and FT4 were further examined if TSH was abnormal. Participants were divided into euthyroid group and subclinical hypothyroidism group. Euthyroid group was further divided into three groups: group A (TSH 0.3-0.99 mIU l(-1)), group B (TSH 1.0-1.9 mIU l(-1)) and group C (TSH 1.91-4.8 mIU l(-1)). Results showed that different levels of serum TSH had no relation with systolic blood pressure (SBP) and diastolic blood pressure (DBP). The prevalence of hypertension in subclinical hypothyroidism group was significantly higher than euthyroid group in females (41.3 vs 25.6%, P<0.05). The risk of hypertension in subclinical hypothyroidism group was significantly higher than that in the euthyroid group after adjusted for age, gender, smoking status, HOMA-IR (homoeostasis model assessment of insulin resistance) and body mass index (odds ratio (OR)=1.753, 95% confidence interval (CI) 1.067-2.879, P=0.027). This association was stronger in females (OR=3.545, 95% CI 1.576-7.975, P=0.004), but there was no statistical significance in males. Within normal range of TSH, both SBP and DBP were similar among the three groups. The prevalence and risk of hypertension were also similar among the three groups. In conclusion, the prevalence of hypertension in subclinical hypothyroidism group was significantly higher than in euthyroid group in females. Change of TSH in normal range did not affect blood pressure.