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Levothyroxine: 21 Million Americans Might be Taking a Hypothyroidism Drug They Don’t Need

Levothyroxine Hypothyroidism Drug

Levothyroxine (also known by its brand name Synthroid) is a widely prescribed medication, with approximately 23 million Americans using it to treat hypothyroidism. It is a condition where the thyroid gland doesn’t produce enough thyroid hormone. Diagnosis of hypothyroidism typically involves measuring thyroid-stimulating hormone (TSH) and free thyroxine (Free T4) levels. However, recent research suggests that these hormone levels naturally fluctuate with the seasons, a factor not accounted for in standard lab tests.

This oversight has led to an alarming number of unnecessary levothyroxine prescriptions, according to Joe El-Khoury, Ph.D., an expert in laboratory medicine. Overuse of Synthroid tablets (levothyroxine) can pose risks, especially for elderly patients over 80, including potentially severe side effects. El-Khoury emphasizes the importance of careful consideration before prescribing levothyroxine, as overtreatment can lead to adverse outcomes. 

The findings underscore the need for more precise diagnostic methods and thoughtful prescribing practices to ensure patient safety. Further, we’ll talk about ‘why levothyroxine may not be effective for everyone. We’ll also discuss whether the TSH test is enough to diagnose hyperthyroidism by understanding the diagnosis criteria for hypothyroidism and how the diagnosis of this condition can be dependent on seasonal factors.

The Study & Its Key Findings on levothyroxine

A study published recently in a journal of The New England Journal of Medicine aimed to understand the effectiveness of a drug commonly used to treat subclinical hypothyroidism. The study asked participants if they had experienced tiredness, exhaustion, or difficulty finding motivation in the past four weeks, symptoms that many people could relate to.

Levothyroxine topped the list of prescription drugs dispensed in the USA due to its prescription widely, surpassing even statins and blood pressure medications. A survey conducted by Johns Hopkins revealed that over 15% of older Americans were taking levothyroxine. Surprisingly, a recent European study showed that in older individuals with mild hypothyroidism, levothyroxine had no notable impact on their symptoms.

Despite its widespread use, the drug’s efficacy in treating this condition has been a topic of debate. This study sought to provide clarity on its effectiveness in older adults with subclinical hypothyroidism. The findings of this study could potentially impact the way this condition is managed and treated, offering valuable insights for healthcare professionals and patients alike.

This finding has validated suspicions among many geriatricians and endocrinologists that levothyroxine might be overprescribed. Dr. Juan Brito from the Mayo Clinic emphasized that while some individuals truly benefit from this medication, the majority may not actually need it.

How Is Hypothyroidism Diagnosed?

The hormone thyrotropin (TSH), produced by the pituitary gland, directs the thyroid to produce hormones crucial for various organs and systems in the body, such as the heart, brain, and muscles. High levels of TSH in the blood suggest that the thyroid gland is not functioning as it should. Typically, doctors request a blood test to check TSH levels when patients report symptoms that could indicate an underactive thyroid, such as fatigue, constipation, weight gain, muscle weakness, or sensitivity to cold. However, in many cases, doctors include TSH readings as part of regular blood tests, even when patients are not showing specific symptoms of thyroid issues. That’s where a game starts or ends! Let’s understand this process in depth:

Diagnosing Process of Hypothyroidism

Hypothyroidism can cause symptoms like tiredness and sadness. In severe cases, it can greatly affect a person’s life. To diagnose hypothyroidism, doctors start by checking the levels of TSH (thyroid-stimulating hormone) in the blood. If TSH is high, they’ll then check the levels of Free T4, a thyroid hormone. If TSH is high and Free T4 is low, a diagnosis of hypothyroidism is made. The treatment typically involves taking a medication called levothyroxine, which helps to replace the missing hormone.

Sometimes, a person might have slightly high TSH but normal Free T4 levels. This is called subclinical hypothyroidism. In some cases, doctors may prescribe levothyroxine to lower TSH levels. However, this approach is not without risks. Research has shown that overtreatment with levothyroxine in patients who might not need it can lead to more harm than good, according to El-Khoury.

A study conducted in 2021 by researchers from the Yale School of Public Health, Mayo Clinic, and the University of Arkansas revealed a concerning finding. Out of the 23 million Americans currently taking levothyroxine, a medication for thyroid issues, around 21 million (approximately 90 percent) might not actually need the prescription. This is worrying because levothyroxine can have side effects such as anxiety, sensitivity to heat, and diarrhea. In extreme cases, it may even lead to serious heart problems and death, particularly in individuals over the age of 80. This information raises important concerns, according to El-Khoury. You can also read this blog if you want to learn more about it– Is it safe to take your thyroid medication when you don’t need it?

Seasonal Influence on Hypothyroidism Diagnosis

According to El-Khoury, a significant factor leading to incorrect hypothyroidism diagnosis is seasonal variation. Typically, levels of TSH, a hormone used to diagnose hypothyroidism, are higher during the winter months. This is also a time when more individuals may experience seasonal affective disorder (SAD) symptoms, which can mimic those of hypothyroidism. Current screening methods do not account for this natural fluctuation, resulting in many individuals being tested and prescribed levothyroxine during a period when their TSH levels are naturally elevated. El-Khoury points out that if these individuals were tested a few months later, their results might fall within the normal range.

The Need for Re-evaluation and Awareness

El-Khoury emphasizes the importance of raising awareness about this issue and encourages healthcare providers to re-test patients at least three months later before starting levothyroxine treatment. He also highlights the need for organizations such as the American Thyroid Association and the American Association for Clinical Chemistry’s AACC Academy to establish a consensus on the clinical decision limit for TSH. The standard used at Yale defines the normal TSH range as 0.27 to 4.2 mIU/L. However, recent studies suggest that levothyroxine may not be beneficial for patients whose levels are naturally below 7.0 mIU/L.

Re-thinking the TSH Range

The idea of raising the upper limit of the normal TSH range from 4.0 mIU/L to 7.0 mIU/L may seem significant. Still, emerging evidence suggests that scientific data no longer supports the current range. This calls for a re-evaluation of existing literature and an acknowledgment of the high biological variability of TSH that has been overlooked for years. El-Khoury urges a reexamination of what is considered normal for TSH levels.

Advice for Patients on Levothyroxine

For those currently taking levothyroxine, El-Khoury advises against stopping the medication without consulting your doctor. He recommends asking your doctor if levothyroxine is truly necessary, especially if your TSH value was less than 7 mIU/L when treatment was initiated. Whether you want to buy your medications from the best Canadian online pharmacy or continue your regimen further, this approach ensures that patients receive appropriate and evidence-based care for their thyroid health. 


The widespread prescription of levothyroxine, including the option to buy Synthroid online, has raised important concerns about overdiagnosis and overtreatment of hypothyroidism. Research suggests that a significant number of patients may be taking this medication unnecessarily, risking potential side effects. Seasonal variations and the current TSH range are factors that require further consideration to ensure accurate diagnosis and appropriate treatment. Patients currently taking levothyroxine should consult with their healthcare provider to ensure their treatment is still necessary, especially if their initial TSH levels were below 7 mIU/L. By re-thinking prescribing practices and diagnostic criteria, we can improve patient safety and optimize thyroid health management.

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