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Stroke risk increases with low-normal TSH levels
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Patients with thyroid-stimulating hormone levels within the upper limit of the reference range have a lower risk for stroke compared with those whose levels are nearer the lower limit, according to recently published findings.
Robin P. Peeters, MD, PhD, of the Rotterdam Thyroid Center, department of internal medicine, department of epidemiology at Erasmus University Medical Center in the Netherlands, and colleagues collected individual participant data from 17 studies identified through a systematic literature search and the Thyroid Studies Collaboration on 43,598 adults with TSH levels within the 0.45 mIU/L to 4.49 mIU/L reference range. Follow-up was a median of 11.6 years and included 449,908 person-years.
Researchers collected data on thyroid function measurements and incident all stroke (combined fatal and nonfatal) and fatal stroke for all participants.
Overall, 2,271 participants had stroke for a 6.3 per 1,000 person-year incidence rate, and 907 had fatal stroke for a 2 per 1,000 person-year incidence rate.
Compared with participants with TSH in the upper limit of the reference range, participants with TSH in the lower limit had a 1.28-fold increased risk for all stroke and 1.2-fold increased risk for fatal stroke.
In the analyses of free thyroxine, the HR for all stroke was 1.08 (95% CI, 0.99-1.15) and 1.1 (95% CI, 1.04-1.19) for fatal stroke.
“Higher TSH levels within the reference range were associated with a lower risk of all stroke,” the researchers wrote. “The analyses for fatal stroke and [free T4] were qualitatively similar. These data provide additional evidence that differences within the reference range of thyroid function, as currently defined, are associated with an increased risk of a major adverse event. Future studies should investigate if re-evaluation if the currently used reference ranges for thyroid function, which are based on fixed biochemical parameters instead of health and treatment outcomes and risk of disease and mortality, should be considered. This is pivotal information when designing randomized controlled trials sufficiently equipped to address possible risks and benefits of thyroid function treatment.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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