Millions of people around the world take thyroid hormone medicine every day to treat an underactive thyroid, also called hypothyroidism.
The thyroid is a small butterfly-shaped gland in the neck, but it has a very important job.
It produces hormones that help control how the body uses energy. These hormones affect the heart, brain, muscles, body temperature, digestion, and many other organs.
When the thyroid does not make enough hormones, people may feel tired, gain weight, become sensitive to cold, and have trouble thinking clearly.
For most people with hypothyroidism, thyroid hormone replacement is a safe and effective treatment. It replaces the hormone that the thyroid can no longer make in sufficient amounts.
With the correct dose, many patients feel much better and can live normal, healthy lives. However, doctors must carefully adjust the amount of medicine because taking too little or too much can create new health problems.
A new study from the University of Michigan suggests that keeping thyroid hormone levels within a healthy range may be especially important for protecting the heart.
The researchers found that people whose thyroid hormone treatment caused hormone levels to become too high or too low had a greater risk of dying from heart-related diseases.
The study included more than 705,000 U.S. veterans who were receiving thyroid hormone therapy, making it one of the largest studies ever carried out on this topic.
Because of the huge number of participants, the researchers were able to examine long-term patterns and better understand how thyroid hormone levels affect heart health.
The team focused on a blood test called thyroid-stimulating hormone, or TSH. TSH is produced by the pituitary gland in the brain and helps control how much hormone the thyroid produces. Doctors routinely use this blood test to check whether thyroid treatment is working properly.
When TSH levels are very low, it often means there is too much thyroid hormone in the body. This condition is known as hyperthyroidism. Too much thyroid hormone can make the heart beat faster and harder than normal. Over time, this may increase the risk of irregular heart rhythms, heart failure, and other serious heart problems.
When TSH levels are very high, it usually means there is not enough thyroid hormone in the body. This is called hypothyroidism. Low thyroid hormone levels can slow many body functions and may also increase the risk of heart disease by affecting blood pressure, cholesterol levels, and the way the heart pumps blood.
The researchers found that patients with TSH levels below 0.1 mIU/L or above 20 mIU/L were more likely to die from heart-related causes than patients whose thyroid hormone levels stayed within the normal range. The results suggest that both extremes can place extra stress on the heart.
The study also found that older adults may face an even greater risk. As people get older, their bodies often become more sensitive to changes in hormone levels. Their hearts may not be able to cope as well with hormone levels that are too high or too low. Because of this, careful monitoring is especially important for older patients receiving thyroid hormone treatment.
To make sure the findings were as reliable as possible, the researchers excluded people with thyroid cancer as well as patients taking medicines such as lithium or amiodarone. These medicines can change thyroid function on their own and could have affected the results. Removing these factors allowed the researchers to more clearly study the effects of thyroid hormone treatment itself.
The findings highlight the importance of keeping thyroid hormone levels in the normal range, a state known as euthyroidism. Reaching this balance is one of the main goals of thyroid treatment.
Doctors usually achieve it by checking blood tests regularly and adjusting the medication dose whenever necessary. Even a small change in dose can sometimes bring hormone levels back into a healthier range.
The study also supports a more personalized approach to treatment. Instead of giving everyone the same dose or aiming for exactly the same hormone levels, doctors may consider a person’s age, overall health, and risk of heart disease when deciding the best treatment plan.
This could help reduce the chances of harmful hormone levels while still treating thyroid disease effectively.
People taking thyroid hormone medicine should not stop or change their medication without speaking to their healthcare provider. Regular blood tests and follow-up appointments remain the safest way to make sure treatment is working properly and to reduce the risk of complications.
The research was conducted by scientists at the University of Michigan and was published in the journal The Journal of Clinical Endocrinology & Metabolism. The findings provide strong evidence that careful management of thyroid hormone therapy is important not only for relieving the symptoms of hypothyroidism but also for protecting long-term heart health.
As more research continues, doctors hope to further improve treatment so patients can safely receive the benefits of thyroid hormone therapy while lowering their risk of heart disease.
If you care about heart health, please read studies about how eating eggs can help reduce heart disease risk, and herbal supplements could harm your heart rhythm.
For more health information, please see recent studies that olive oil may help you live longer, and vitamin D could help lower the risk of autoimmune diseases.
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