High serum thyrotropin levels are associated with current but not with incident hypertension.

Background: Recent data from a population-based study in children and adolescents suggest that serum thyrotropin (TSH) levels are associated with arterial blood pressure and hypertension. These results are in agreement with some but not all population-based studies in adults. Discrepancies in results might be explained by drug intake, different iodine supplies, and sizes of populations investigated. In addition, it is not clear whether an association between TSH and hypertension exists longitudinally or only cross-sectionally. Thus, our aim was to investigate cross-sectional and longitudinal associations between thyroid function and arterial blood pressure in a large consortium of cohort studies in adults.

Methods: Data from five population-based studies were pooled resulting in 17,023 individuals being available for cross-sectional and 10,048 individuals for longitudinal analyses. Associations of baseline TSH with baseline blood pressure or hypertension were analyzed by multivariable median or logistic regression models. Multivariable median or Poisson regression models were used to investigate associations of baseline TSH with five-year change in arterial blood pressure or incident hypertension.

Results: There was a cross-sectional positive association of TSH with arterial blood pressure (p<0.001) and hypertension (odds ratio [OR]=1.76 [confidence interval (CI) 1.24-2.50], p=0.002). Likewise, hypothyroidism was associated with systolic (β=1.1 [CI 0.1-2.1], p=0.040) and diastolic blood pressure (β=1.4 [CI 0.7-2.0], p<0.001). TSH, however, was not consistently associated with a five-year change in blood pressure or incident hypertension.

Conclusions: High serum TSH levels were associated with current hypertension and blood pressure but not with a five-year change in blood pressure and incident hypertension. This argues for only a short-term effect of thyroid hormone levels on arterial blood pressure or a spurious association that needs further evaluation in population-based studies.