Associations Between Thyroid and Blood Pressure in Euthyroid Adults: A 9-Year Longitudinal Study

Area of Science:

• Endocrinology
• Cardiovascular Health
• Epidemiology

Background:

• Limited research exists on thyroid function within the reference range (RR) and blood pressure (BP).
• Contradictory findings complicate understanding the relationship between thyroid hormones and BP.
• Longitudinal data on thyroid function and incident hypertension are scarce.

Purpose of the Study:

• To investigate associations between serum thyrotropin (TSH) and free T4 (FT4) within the RR and BP components.
• To examine the relationship between TSH and FT4 and the incidence of prehypertension (preHTN) and hypertension (HTN).
• To analyze these associations over a 9-year follow-up period in a population-based cohort.

Main Methods:

• Utilized data from 2282 euthyroid individuals in a population-based cohort study.
• Employed sex-stratified multivariate generalized estimating equation (GEE) for longitudinal BP trends.
• Applied a multivariate transitional model to assess incident preHTN and HTN, considering prior BP status.

Main Results:

• A general decreasing trend in systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and pulse pressure (PP) was observed over 9 years.
• Serum FT4 within the RR positively correlated with all BP parameters in the total population and men.
• Higher FT4 (1 ng/dl) was associated with a 40% increased risk of preHTN (OR 1.40), but not HTN (OR 0.93). Serum TSH showed a mild increasing effect on men's SBP, DBP, and MAP.

Conclusions:

• Serum FT4 within the RR demonstrates a stronger association with BP parameters than TSH.
• The observed associations between FT4 and BP are not consistent between sexes.
• Elevated FT4 levels within the reference range are linked to an increased risk of developing prehypertension.