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The following is a summary of “Endogenous and Exogenous Thyrotoxicosis and Risk of Incident Cognitive Disorders in Older Adults,” published in the October 2023 issue of Internal Medicine by Adams, et al.

Thyroid hormone is a popular US prescription, and 20% may be overtreated. Endogenous hyperthyroidism may cause dementia. However, iatrogenic thyrotoxicosis evidence is scarce.

For a study, researchers sought to examine whether endogenous and exogenous thyrotoxicosis increases cognitive problem risk. The cohort research examined electronic health data for Johns Hopkins Community Physicians Network primary care participants from January 1, 2014, to May 6, 2023. Seniors 65 and older with two primary care visits 30 days apart were eligible. No patients (65,931) had a history of low TSH or cognitive impairment within 6 months of their initial visit. The data was analyzed from January 1 to August 5, 2023.  Depending on the clinical situation, low TSH levels, barring acute sickness or drugs, were attributed to endogenous, exogenous, or unknown causes. 

To increase sensitivity and account for primary care dementia underdiagnosis, cognitive disorders, including mild cognitive impairment and all-cause dementia, were the end measure. Among 65,931 patients, the median age at the initial visit was 68.0 years (IQR: 65.0-74.0 years); 56% were female, and 69.9% were White. Patients exposed to thyrotoxicosis had 11.0% (95% CI, 8.4%-14.2%) cognitive problem incidence by age 75, compared to 6.4% (6.0%-6.8%) for those not exposed. 

A substantial association exists between all-cause thyrotoxicosis and cognitive problem diagnosis across age groups (adjusted hazard ratio, 1.39; 95% CI, 1.18-1.64; P < .001). After stratifying by cause and severity, with dose-related point estimates, exogenous thyrotoxicosis remained a significant risk factor (adjusted hazard ratio, 1.34; 95% CI, 1.10-1.63; P = .003). Low TSH levels from endogenous or exogenous thyrotoxicosis were related to greater cognitive disorder risk in 65-year-olds in this cohort research. Thyroid hormone treatment often causes iatrogenic thyrotoxicosis. Understanding the risks of overtreatment is crucial for treating thyroid hormone, one of the most often prescribed drugs in the US.

Source: jamanetwork.com/journals/jamainternalmedicine/article-abstract/2811088