High Thyroid Hormone Levels Associated with Arterial Disease

Atherosclerosis is the process of progressive thickening and hardening of the walls of arteries from fat deposits on their inner lining. Atherosclerosis progresses insidiously from a subclinical condition to the clinical onset of vascular events to death.

High and high-normal levels of a thyroid hormone called free thyroxine 4 (FT4), are associated with artery disease and death in elderly and middle-aged people. FT4 is a hormone produced by the thyroid gland that helps control the rate at which the body uses energy.

Medical scientists at the Erasmus Medical Center (Rotterdam, The Netherlands) carried out a prospective population-based cohort study that investigated the determinants, occurrence and progression of chronic diseases in the middle-aged and elderly. Baseline measurements for the study were performed during the third visit of the first cohort of 4,797 and the first visit of the second of group of 3,011 and third cohort of 3,932 in the Rotterdam Study.

Thyroid function was assessed at baseline in three study cohorts using the same method and assay. Measurements of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase antibodies (TPOAb) were performed in baseline serum samples stored at -80 °C using the electrochemiluminescence immunoassay ECLIA. The reference ranges of serum TSH (0.40–4.0 mIU/L) and serum FT4 (0.86–1.94 ng/dL; equivalent to 11–25 pmol/L) were determined.

The team found that after a median follow-up of 8.8 years, there were 612 atherosclerosis-related cardiovascular deaths and 934 first-time atherosclerosis-related cardiovascular events. Increasing FT4 levels were associated with twice the odds of having high levels of coronary artery calcification scores, which may be an indicator of subclinical atherosclerosis; 87% greater risk of suffering an atherosclerosis-related cardiovascular event; and double the risk of atherosclerosis-related cardiovascular death. The authors conclude that FT4 levels in middle-aged and elderly subjects were positively associated with atherosclerosis throughout the whole disease spectrum, independently of cardiovascular risk factors.

Arjola Bano, MD, MSc, DSc, the lead study author, said, “We expected that thyroid function would influence the risk of developing atherosclerosis by affecting cardiovascular risk factors such as blood pressure. However, our results remained very similar after accounting for several cardiovascular risk factors. This suggests that mechanisms other than traditional cardiovascular risk factors may play a role. Our findings suggest that thyroid hormone FT4 measurement can help identify individuals at increased risk of atherosclerosis.” The study was published on October 31, 2017, in the journal Circulation Research.

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