The association between subclinical hyperthyroidism and blood pressure in a population-based study

Objective Although evidence for an increased risk of hypertension in both overt hyperthyroidism and overt hypothyroidism is consistent, the relation between subclinical hyperthyroidism and blood pressure has not yet received sufficient attention. Methods The Study of Health in Pomerania is a population-based survey in Germany that was conducted in a previously iodine-deficient region. A study population of 4087 subjects (2050 women) without overt hyperthyroidism or increased serum thyrotropin levels was available for the present study. Serum thyrotropin levels < 0.25 mIU/l and < 0.1 mIU/l were considered decreased and suppressed, respectively. Results Multivariable analyses revealed lower adjusted mean values for systolic blood pressure in subjects with decreased [ 132.9 mmHg, 95% confidence interval (CI) = 131.1 mmHg; 134.8 mmHg] versus normal serum thyrotropin levels (135.0 mmHg, 95% CI = 134.4 mmHg; 135.6 mmHg, P = 0.04). The adjusted mean values for diastolic blood pressure and pulse pressure did not differ significantly between both groups. Analyses that were performed after all subjects receiving antihypertensive medications had been excluded did not reveal any statistically significant associations between decreased serum thyrotropin levels and the endpoints investigated. There was also no association of suppressed serum thyrotropin levels with blood pressure or hypertension. Conclusion It is concluded that subclinical hyperthyroidism, as demonstrated by decreased as well as suppressed serum thyrotropin levels and serum free thyroid hormone levels within the reference range, is not associated with hypertension.