Associations of TSH levels within the reference range with future blood pressure and lipid concentrations: 11-year follow-up of the HUNT study

Abstract

Objective: In cross-sectional studies, TSH levels within the reference range have been positively associated with blood pressure and adverse serum lipid levels. In a prospective study, we aimed to determine whether differences in TSH levels within the reference range are associated with future levels of blood pressure and lipids. Design: We conducted a prospective population-based study. Methods: In 9709 women and 4644 men without previous thyroid disease who had a baseline TSH level of 0.45-4.5 mU/l, we studied the associations of baseline TSH levels with blood pressure and lipid levels at follow-up 11 years later. Results: Higher TSH levels at baseline were associated with higher systolic (PZ0.002 in women) and diastolic (PZ0.03 in women) blood pressure, non-HDL cholesterol (PZ0.01 in men) and triglyceride (PZ0.008 in men) levels and lower HDL cholesterol levels (P!0.001 in women and men) at followup, but the associations were very modest and not consistent between the sexes. Among people who remained free of thyroid disease, changes in TSH levels during follow-up were associated with concomitant changes in systolic and diastolic blood pressure, non-HDL cholesterol and triglyceride levels (all P!0.001), with similar results being observed for women and men. Thus, blood pressure and lipid levels increased among people with an increase in TSH levels and decreased among people with a decrease in TSH levels compared with people with no change in TSH levels. Conclusions: High TSH levels within the reference range may be associated with modestly higher future levels of blood pressure and adverse serum lipids. TSH levels may co-vary with blood pressure and lipid levels among people with apparently normal thyroid function.

Subclinical hypothyroidism: a historical view and shifting prevalence

“…Across studies, the prevalence of SCH (like overt hypothyroidism) is consistently higher in women than in men (Table 2) (17)(18)(19)(20)(21)23,25,27,(29)(30)(31)(32)(33)(34)(35)(36)(37)(38). In the Whickham study, the prevalence of SCH in women was 7.5%, nearly three times the prevalence in men (2.8%) (19).…”

“…In a recent study, Asvold and colleagues reported that the prevalence of untreated SCH in Norway decreased over an 11-year period from 1995 to 1997 (HUNT 2 study) to 2006-2008 (HUNT 3 study) (25). In HUNT 2 and HUNT 3, SCH was defined as TSH > 4.5 mIU/l combined with normal levels of FT4.…”

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

“…Iqbal et al in a study of a population of 5 872 euthyroid patients in the Tromso study, found a positive association between TSH and systolic and diastolic blood pressure; they reported that only diastolic hypertensive patients have higher serum TSH levels. In an 11 year follow-up study of 14 353 individuals with serum TSH levels within reference range higher TSH levels at the baseline were associated with elevated levels of blood pressure at follow-up, but the strength of the associations suggested that the findings may not be clinically relevant [25].…”

Thyroid Dysfunction and Blood Pressure Components: Multivariate Statistical Associations

“…Moreover, to date, a series of contradictory relationships have been noted. Indeed, a linear relationship between serum TSH levels and BP (both systolic and diastolic) was observed by Asvold, et al [5,6]. However, no such associations were observed in two further stud-…”