Thyrotoxicosis linked to risk for incident cognitive disorder

For older adults, exposure to a low thyrotropin (TSH) level from either endogenous or exogenous thyrotoxicosis is associated with an increased risk for incident cognitive disorder, according to a study recently published in JAMA Internal Medicine.

Roy Adams, Ph.D., from the Johns Hopkins University School of Medicine in Baltimore, and colleagues conducted a cohort study to examine whether thyrotoxicosis is associated with an increased risk for cognitive disorders. Patients aged 65 years and older with at least two visits to their primary care physicians 30 days apart were eligible; the analysis included 65,931 patients. The exposure variable was low TSH level, characterized based on the clinical context as due to endogenous thyrotoxicosis, exogenous thyrotoxicosis, or unknown cause.

The researchers found that the incidence of cognitive disorder was 11.0 and 6.4 percent by age 75 years for patients exposed and not exposed, respectively, to thyrotoxicosis. Across age groups, all-cause thyrotoxicosis was associated with the risk for cognitive disorder diagnosis after adjustment (adjusted hazard ratio, 1.39). Exogenous thyrotoxicosis remained a significant risk factor when stratified by cause and severity (adjusted hazard ratio, 1.34), with point estimates indicating a dose response.

“An increased risk of cognitive disorders is among the potential negative consequences of thyroid hormone excess, a common consequence of thyroid hormone treatment,” the authors write.

One author disclosed ties to the biopharmaceutical industry.

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