Even Within the Normal Range, Higher Thyroxine Levels Correlate with Earlier Mortality

Some studies suggest that patients with high-normal thyroid function have excess risk for cardiovascular disease (CVD) and early death. In this population-based Dutch cohort study, 7785 adults (mean age, 65) without known thyroid disease (thyrotropin and free thyroxine [FT₄] within normal reference ranges) were identified. Patients were divided into tertiles according to both thyrotropin and FT₄ levels.

During median follow-up of 8.1 years, fatal or nonfatal adverse CVD events occurred in 10% of patients, and 17% died overall. Outcomes were as follows:

• People in the highest FT₄ tertile had 32% higher risk for incident CVD.

• People in the highest FT₄ tertile were ≈50% more likely to die than people in the lowest tertile.

• People in the lowest FT₄ …