A new study from Johns Hopkins Medicine has found that having too much thyroid hormone in the body may increase the risk of memory and thinking problems in older adults. This condition, called thyrotoxicosis, happens when the thyroid gland makes too much hormone or when someone takes too much thyroid medication.
Thyroid hormones help control how the body uses energy, known as metabolism. They are essential for many body functions, including heart rate, body temperature, and brain activity.
But when there is too much of these hormones, it can cause health problems—especially in seniors. One serious concern is how it may affect the brain and increase the risk of cognitive disorders, including memory loss or confusion.
Previous studies suggested a possible connection between high thyroid levels and cognitive decline, but the results were not always clear. Some studies only looked at people who had thyroid disease and did not include those taking thyroid hormone as medication.
To better understand this link, researchers at Johns Hopkins studied the health records of nearly 66,000 people aged 65 and older who received care between 2014 and 2023.
The average age at the start of the study was 71. The researchers made sure that each person had at least two doctor visits spaced over a month apart, to track changes over time.
They found that people with thyrotoxicosis had a 39% higher risk of being diagnosed with a cognitive disorder, compared to people with normal thyroid hormone levels. This increased risk was found in both people with thyroid disease and those taking too much thyroid medication.
By age 75, 11 out of every 100 people with thyrotoxicosis had been diagnosed with a cognitive disorder, compared to just over 6 out of 100 people without the condition. By age 85, about one-third of people with too much thyroid hormone had cognitive issues, compared to one-fourth of those without.
The study also found that the more excess hormone in the body, the higher the risk. People with very high thyroid levels had a 65% greater risk of cognitive problems, while those with moderately high levels had a 23% greater risk.
These findings are important for doctors, especially when prescribing thyroid medication to older adults. Sometimes, older people with low thyroid function are given hormone replacement therapy.
But if the dose is too high, it could lead to harmful side effects, including problems with memory and thinking. Doctors need to be careful with dosing, especially in seniors, and should follow age-specific treatment guidelines to avoid giving too much.
The study emphasizes the importance of regular check-ups and blood tests to monitor thyroid hormone levels, especially in older adults who are more vulnerable to both hormone imbalance and cognitive decline.
More research is needed to fully understand why too much thyroid hormone affects brain health, but this study is a big step in showing the importance of balanced treatment. The full results were published in JAMA Internal Medicine and offer valuable information for both patients and healthcare providers.
In short, while thyroid hormones are essential for health, too much of them—especially in older age—can do more harm than good. Careful treatment and monitoring may help protect the brain and reduce the risk of memory problems in later life.
If you care about brain health, please read studies about inflammation that may actually slow down cognitive decline in older people, and low vitamin D may speed up cognitive decline.
For more information about brain health, please see recent studies about common exercises that could protect against cognitive decline, and results showing that this MIND diet may protect your cognitive function, prevent dementia.
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