Initial thyroid status and cardiovascular risk factors: the EPIC-Norfolk prospective population study.

CONTEXT: Thyroid status affects several aspects of cardiovascular risk profile, including lipid levels and blood pressure. Whether thyroid status affects the risk of coronary heart disease (CHD) and all-cause mortality remains controversial.

DESIGN: The EPIC-Norfolk prospective population study. Mean follow-up was 10.6 years.

PATIENTS: Study participants were 11 554 men and women aged 45-79 years, who were living in Norfolk, UK.

MEASUREMENTS: Baseline cardiovascular risk factors were recorded and concentrations of thyroid-stimulating hormone (TSH) and free thyroxine (FT4) were measured in baseline samples. Regression analyses were performed to assess the association between thyroid hormone levels and cardiovascular risk factors. A proportional hazards model was used to estimate the risk of CHD and all-cause mortality by baseline thyroid status. No information was available on thyroid treatment during follow-up.

RESULTS: Thyroid abnormalities were common, particularly among women. Thyroid abnormalities were associated with an altered cardiovascular risk profile. Even within the normal range, thyroid hormone levels, TSH more strongly than FT4, were associated with lipid levels and blood pressure among both men and women. We did not observe a significant association between subclinical thyroid abnormalities and risk of CHD or all-cause mortality.

CONCLUSIONS: Despite the association between thyroid hormone levels and cardiovascular risk factors, thyroid status was not statistically significantly associated with the risk of future CHD or all-cause mortality in this large cohort.