Healio
Healio
May 21, 2014
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Thyroid hormones may not play role in deaths from cancer, CVD

In euthyroid men and women, serum free thyroxin and free triiodothyronine levels are inversely associated with deaths from cancer and not associated with deaths from cardiovascular disease, according to research published in The Journal of Clinical Endocrinology & Metabolism.

In the Kangbuk Samsung Health Study in South Korea — the largest population-based cohort study to date evaluating the association between thyroid hormones and mortality endpoints — Yiyi Zhang, PhD, and fellow researchers looked at 212,456 adults (124,976 men, 87,480 women) with normal thyroid hormone levels and no history of thyroid disease at baseline. All participants had received a health examination between 2002 and 2009.

Yiyi Zhang, PhD

Yiyi Zhang

Data were collected for demographics, smoking status, alcohol consumption, medical history and medication use though self-administered questionnaires. Cholesterol, insulin, glucose, creatinine, albumin and C-reactive protein were quantified. Using radioimmunoassay, the researchers measured free T4, free T3 and thyroid-stimulating hormone in participants to examine the prospective association between levels and mortality endpoints.

At follow-up (mean, 4.3 years), 730 participants had died. Data from death certificates showed 335 cancer deaths and 112 CV deaths; the researchers evaluated site-specific cancer mortality for cancers with at least 20 deaths. Comparing the highest vs. lowest quartile, free T4 was inversely associated with all-cause mortality (HR=0.77; 95% CI, 0.63-0.95), and free T3 was inversely associated cancer mortality, particularly from liver cancer (HR=0.62; 95% CI, 0.45-0.85). TSH was not associated with mortality endpoints.

The researchers highlighted a few limitations to the study, including a relatively short follow-up period, having no measurements for thyroid antibodies and examining a population of generally healthy middle-aged people.

“Further research is needed to confirm these findings in other ethnic groups to better understand the underlying mechanisms between thyroid hormones and cancer mortality, and to evaluate the role of thyroid hormone supplementation in participants with low-normal levels of thyroid hormones,” the researchers wrote.

Disclosure: The researchers report no relevant financial disclosures.

Sources/Disclosures

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Source: Zhang Y. J Clin Endocrinol Metab. 2014;doi:10.1210/jc.2013-3832.