Excess thyroid hormone linked to cognitive decline in older adults

A recent study from Johns Hopkins Medicine highlights a concerning link between thyrotoxicosis—a condition caused by excess thyroid hormone—and an increased risk of cognitive disorders in older adults.

Thyrotoxicosis can arise from two main sources: exogenous thyrotoxicosis, which is caused by taking too much thyroid medication, and endogenous thyrotoxicosis, which occurs due to thyroid-related conditions like hyperthyroidism or Graves’ disease.

Thyroid hormones play a vital role in maintaining the body’s metabolism and other essential functions. However, when thyroid hormone levels are too high, they can lead to various health complications.

While past research hinted at a connection between thyrotoxicosis and cognitive decline, the evidence was incomplete, often excluding cases related to excessive medication use. To address this gap, Johns Hopkins researchers conducted a comprehensive study to examine both forms of thyrotoxicosis and their impact on cognitive health.

The study analyzed electronic health records of 65,931 adults aged 65 and older who received care within the Johns Hopkins Health System from 2014 to 2023. The average age of participants at their first recorded visit was 71, and all patients had at least two medical visits spaced 30 or more days apart.

The results showed that thyrotoxicosis, whether caused by thyroid disorders or excessive thyroid hormone treatment, was associated with a 39% higher risk of cognitive disorders compared to individuals without the condition.

This risk increased with age. By age 75, 11% of patients with thyrotoxicosis had been diagnosed with a cognitive disorder, compared to 6.4% of those without the condition. By age 85, the gap widened further, with 34% of thyrotoxicosis patients receiving a cognitive disorder diagnosis compared to 26% of those without the condition.

The study also revealed that the severity of excess thyroid hormone influenced the level of cognitive risk. Among patients prescribed thyroid hormone therapy, those with severe hormone excess had a 65% greater risk of cognitive disorders, while those with moderate excess faced a 23% higher risk.

These findings have significant implications for how thyroid hormone therapy is managed, particularly in older adults. While thyroid hormone treatments are essential for many patients, overtreatment can lead to unintended health risks, including cognitive decline.

The researchers emphasized the need for healthcare providers to carefully tailor thyroid hormone therapy to avoid excessive doses, especially in older patients. Following age-appropriate treatment guidelines could help reduce the risk of cognitive complications.

This study sheds light on the potential long-term consequences of thyroid hormone levels on brain health and provides valuable insights for healthcare professionals treating thyroid-related conditions. More research is needed to better understand the mechanisms behind these effects and refine treatment strategies to minimize risks.

The findings were published in JAMA Internal Medicine. For more information, you can explore recent studies on thyroid health, cognitive disorders, and related topics in aging and metabolism.

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