Thyroid Dysfunction Increases Cardiovascular Risks in Diabetic Dialysis Patients

Though dialysis patients have a greater risk for thyroid disorders due to uremic toxins, protein malnutrition, and inflammation, the prevalence of those disorders and their impact on cardiovascular (CV) events and mortality have not been investigated.

To analyze whether subclinical thyroid disorders are associated with CV events and mortality, a group of researchers conducted a large prospective cohort study involving 1,000 diabetic hemodialysis patients from 178 centers in Germany.

The authors examined thyroid status and clinical outcomes over a period of 4 years, during which they looked for sudden cardiac death, myocardial infarction (MI), stroke, combined CV events, and overall mortality. As they gathered more data, the researchers compared short-term cardiac incidents in the first year to episodes that occurred after the 2-year mark. One strength of the study was that it measured free triiodothyronine (T3) and tetraiodothyronine (T4) in addition to thyroid-stimulating hormone (TSH).

The investigators detected euthyroidism in 78.1% of patients, subclinical hyperthyroidism in 13.7%, and subclinical hypothyroidism in 1.6%. Approximately 5% of patients displayed euthyroid sick syndrome (ESS), which presents as low circulating T3 levels in those with normal or slightly decreased TSH and T4 concentrations.

Though clinicians have historically considered ESS to be an adaptation to protein and energy wasting in critical illness, rather than a true thyroid disease, ESS has been associated with poor prognosis in severely ill patients with sepsis, chronic heart failure (CHF), or liver cirrhosis. In this study, dialysis patients with subclinical hyperthyroidism or ESS had more than double the adjusted short-term risk of sudden cardiac death, compared to those with euthyroidism. Short-term mortality was increased almost 3-fold for ESS patients, but that effect was absent over the long term.

Subclinical hypothyroidism was not associated with CV events, all-cause mortality, stroke, or MI, and the latter two conditions were also not affected by subclinical hyperthyroidism.

In light of their overall findings, the authors encouraged regular assessment of thyroid status in diabetic dialysis patients to estimate their cardiac risk.