Thyroid Function, Cardiovascular Risk Factors, and Incident Atherosclerotic Cardiovascular Disease: The...

Cardiovascular outcomes in mild thyroid dysfunction (treatment controversial) and moderate or severe dysfunction (treatment standard) remain uncertain.

To examine cross-sectional and prospective associations of thyroid function with cardiovascular risk factors and events.

In the Atherosclerosis Risk in Communities Study, we measured concentrations of thyrotropin, free thyroxine, and total triiodothyronine (T3) in stored serum samples originally collected in 1990-1992. We used multivariable linear regression to assess cross-sectional associations of thyroid function with cardiovascular risk factors and Cox regression to assess prospective associations with cardiovascular events. Follow-up occurred through 31 December 2014.

General community.

Black and white men and women from the United States, without prior myocardial infarction (MI), stroke, or heart failure.

Cross-sectional outcomes were blood pressure, glycemic markers, and blood lipids. Prospective outcomes were adjudicated fatal and nonfatal MI and stroke.

Among 11,359 participants (57 ± 6 years, 58% women), thyroid function was more strongly associated with blood lipids than blood pressure or glycemic measures. Mean adjusted differences in low-density lipoprotein cholesterol were +15.1 (95% confidence interval: 10.5 to 19.7) and +3.2 (0.0 to 6.4) mg/dL in those with moderate/severe and mild chemical hypothyroidism, relative to euthyroidism; an opposite pattern was seen in hyperthyroidism. Similar differences were seen in triglycerides and non-high-density lipoprotein cholesterol. With a 22.5-year median follow-up, 1102 MIs and 838 strokes occurred, with similar outcomes among baseline thyroid function groups and by T3 concentrations.

Hypothyroidism is associated with hyperlipidemia, but the magnitude is small in mild chemical hypothyroidism, and cardiovascular outcomes are similar between thyroid function groups.