The Association Between Blood Pressure and Normal Range Thyroid Function Tests in a Population Based Tehran Thyroid Study

Several studies have shown an association between overt hypothyroidism and diastolic hypertension. Association between subclinical hypothyroidism and hypertension is a matter of debate. The aim of this study was to examine the association of systolic and diastolic blood pressure, pulse pressure and mean arterial blood pressure with serum thyroid hormones levels in euthyroid subjects. Data from 4756 individuals of the Tehran Thyroid study (TTS) without any previously known thyroid disease were analyzed. We divided participants based on TSH tertiles. Serum TSH and free T4 (FT4) concentration, systolic blood pressure (SBP), diastolic blood pressure (BPD) body mass index (BMI) were measured in all subjects. Among 5786 individuals participated, 4985 were euthyroid. After implementing exclusion criteria, 4756 individuals remained of whom 2122 (44.6%) were male and 2634 (55.4%) were female. Multiple linear regression analysis revealed no association between TSH levels within reference ranges and blood pressure profile. No significant relationship was observed between TSH levels and systolic or diastolic blood pressure or the mean arterial pressure or pulse pressure in each tertile of TSH. There was a negative association between pulse pressure and TSH in the second tertile (r=-0.066, p=0.009). Regression analysis showed that FT4 was significantly associated with systolic blood pressure, diastolic blood pressure, pulse pressure and mean arterial pressure. No association was found between serum TSH and blood pressure profile in euthyroid subjects. Serum FT4 levels showed a positive association with blood pressure profiles.