Community-based study of the association of subclinical thyroid dysfunction with blood pressure

Abstract

The relationship between subclinical thyroid dysfunction and blood pressure has been controversial and received unsufficient attention. Thus, we performed a cross-sectional study conducted among 6,992 inhabitants from six districts of Jiangsu Province to investigate the association of subclinical thyroid dysfunction with blood pressure in China. The data from 6,583 subjects (4,115 women and 2,468 men) were included and divided into three groups: euthyroidism (n = 5669, 86.11%), subclinical hyperthyroidism (n = 108, 1.65%), and subclinical hypothyroidism (n = 806, 12.24%). In the groups with subclinical hypothyroidism and hyperthyroidism, systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure were not significantly different from those in the groups with euthyroidism after being adjusted for age, sex, BMI, and smoking status (P > 0.05). More extensively, the SBP and DBP in the group of subclinical hypothyroidism with lower level of TSH (TSH 4.51-10.00 mIU/l, SCH(1)) were significantly higher than those of participants with euthyroidism (P < 0.05). Multivariable logistic analysis revealed that subclinical hypothyroidism with lower TSH (TSH 4.51-10.00 mIU/l) was an independent risk factor for increased SBP (OR = 1.28, 95% CI 1.03-1.59, P = 0.028). Similar results could not be found between groups of euthyroid and subclinical hypothyroid with higher level of TSH (TSH > 10 mIU/l, SCH(2)). Further subdivision of the euthyroid group on the basis of a TSH cut-off of 2.5 mIU/l, revealed still no significant difference in blood pressure after adjustment regardless of whether the TSH levels were in the lower reference (TSH 0.40-2.50 mIU/l, n = 4093) or in the upper reference ranges (TSH 2.51-4.50 mIU/l, n = 1576) (P > 0.05). We concluded that subclinical thyroid dysfunction was not associated with blood pressure. Neither subclinical hyperthyroidism nor subclinical hypothyroidism independently predicted increased blood pressure.

Blood pressure levels in patients with subclinical thyroid dysfunction: a meta-analysis of cross-sectional data

“…Our review yielded seven large cross-sectional studies [5][6][7][8][9][10][11] (including subclinical hypothyroidism and subclinical hyperthyroidism). These studies reported the number of patients with a diagnosis of subclinical thyroid dysfunction at baseline.…”

“…The normal free T4 range of 0.6-1.9 ng dl -1 was used in most studies. [5][6][7][8][9][10][11] The TSH reference range is a topic of debate; however, TSH levels are critically important in diagnosing subclinical disease. Subclinical hypothyroidism is defined as the presence of an elevated TSH and a normal T4 level.…”

“…Participants with overt thyroid dysfunction were also excluded. 5 Participants with a history of thyroid disease and those who were taking medication affecting thyroid function, 6,7 those who were diagnosed with hypothyroidism or hyperthyroidism in this investigation as well as participants with hypertension who had taken oral antihypertensive drugs in the previous 4 weeks were also excluded. 6 Participants with any thyroid disease 8 and who were being treated for thyroid disease and hypertension were also excluded.…”

“…4 Within the past 5 years, six large cross-sectional studies on this topic have produced conflicting results. [5][6][7][8][9][10] Three studies concluded that subjects with subclinical hypothyroidism had a significantly higher systolic blood pressure (SBP) than euthyroid subjects (age, sex and body mass index adjusted). 5,9,10 However, discrepancies between study results may have arisen from differences in the level of adjustment for other cardiovascular risk factors among the included studies.…”

“…Subclinical hyperthyroidism has been associated with decreased blood pressure level, 9 but with conflicting data. 5,7,10,11 There have been no analyses performed to date on the relationship between subclinical thyroid dysfunction and blood pressure. To determine whether subclinical thyroid dysfunction is associated with increased blood pressure, we performed a meta-analysis of crosssectional studies that examined the relationship between subclinical thyroid dysfunction and the risk of increased blood pressure levels.…”