Can You Have Hypothyroidism With Normal TSH Levels?

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If you have hypothyroidism with normal TSH levels, you may still experience symptoms even though your thyroid stimulating hormone (TSH) blood test levels are well within range. Most people whose thyroid works normally have a TSH between 0.4 mU/L and 4.0 mU/L, but there can be variations in "normal" levels and symptoms.

The reasons for this are complex. TSH test levels can vary due to causes as simple as medication you take or the time of day. Low levels may reveal a subclinical hypothyroidism that isn't treated even though you experience fatigue, muscle pain, and other symptoms. Other concerns may require treatment, typically with levothyroxine.

This article explains why it's possible to have hypothyroidism with a normal TSH level. It will help you to understand your TSH test results and the care decisions you and your healthcare provider make.

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5 Common Misconceptions About Thyroid Disease

Causes of Hypothyroidism Symptoms With Normal TSH Levels

Hypothyroidism with normal TSH levels can still lead to common symptoms of low thyroid function. These symptoms can include:

  • Chronic fatigue
  • Weight gain despite no change in diet
  • Slow heart rate
  • Shortness of breath with exertion (exercise)
  • Feeling cold all the time
  • Muscle and joint aches
  • Constipation

There are two main types of conditions—primary and secondary hypothyroidism—that may be at play.

Endocrine Function

Other hormones work with TSH to help regulate processes in your body. For example, the pituitary gland is where TSH is produced. The pituitary may increase TSH production in response to low levels of thyroid hormone production in the thyroid gland. This can cause TSH levels to be higher.

Pituitary failure can be caused by a tumor or injury, bleeding at the site, an infection, or an inflammation called hypophysitis. Similar interactions can occur with the hypothalamus, which sits near the pituitary gland and affects thyrotropin-releasing hormone (TRH) production.

TSH isn't actually a thyroid hormone. It's produced in the pituitary gland and acts on the thyroid. TSH levels tell only a part of the story in terms of thyroid function, symptoms, and treatment.

Pregnancy

Physical changes during pregnancy also lead to changes in thyroid hormone levels, and the reference range of what's considered normal may be different for this reason. Your TSH levels can be lower during the first trimester. Or, high estrogen levels may increase thyroid hormone levels.

While hyperthyroidism (as with Graves' disease) is a concern, so is hypothyroidism. There's some evidence of a higher risk of pregnancy loss, and increased risk of gestational hypertension (high blood pressure) and preeclampsia (hypertension with high protein levels in urine), which can lead to premature delivery and low birth weight.

Low levels of thyroid in a pregnant person also can affect thyroid and brain development in the fetus. Treatment isn't always necessary but a healthcare provider may prescribe levothyroxine (LT4).

Medication

Certain medications, including corticosteroids like prednisone, can lead to hypothyroidism despite normal TSH levels. Some studies suggest vitamin D levels also may have an impact.

So can alternative treatments for thyroid conditions for which there is no evidence of benefit. Some of these concerning options used for hypothyroidism include:

  • High-iodine herbal remedies
  • Selenium
  • Iodine-tyrosine supplements
  • Kelp (a kind of seaweed)

The American Thyroid Association cautions that too much iodine can worsen both hypothyroidism and hyperthyroidism, and using unproven remedies can prevent people from getting treatment that they really need.

Cancer Treatments

Hypothyroidism can be due to radiation therapy for head and neck cancers. One study of 233 people who received radiation treatments for these cancers found 29% experienced hypothyroidism due to the radiation.

This appeared to be more common in younger people and those assigned female at birth.

Levothyroxine Response

People who take LT4 for a hypothyroid disorder typically have blood tests to monitor their TSH and total thyroxine (T4) levels. The assumption is that a normal T4 level, one that's been corrected by medication, will mean the related process the body uses to make triiodothyronine (T3) also will occur normally.

But it doesn't always happen. Some people who take LT4 still won't have more of the active and necessary T3 form in their bodies. Researchers who studied people taking LT4 found they have a lower T3 to T4 ratio in the body than the general population. This may mean that people still have symptoms despite "normal" TSH.

Managing Hypothyroidism Fatigue

Verywell / Shideh Ghandeharizadeh

Managing Hypothyroidism Symptoms With Normal TSH Levels

Research shows that some people with hypothyroidism can have normal TSH levels on standard blood work. Thus, their hypothyroidism can be missed by healthcare providers.

People who have normal TSH levels but still experience symptoms of hypothyroidism should speak to their providers about their concerns. They also can take steps to better manage fatigue and other symptoms, including:

  • Getting a healthy amount of rest
  • Eating a balanced diet
  • Setting fitness goals and staying active
  • Managing other health conditions, like diabetes
  • Managing stress levels

Do You Need a New TSH Target?

When assessing your response to treatment, many healthcare providers will aim to get your TSH level to around 1 to 2 mU/L—the lower end of the normal range.

To this end, some endocrinologists have lowered the TSH threshold from the standard normal range to a revised and lower normal range. This may mean you are less prone to symptoms.

While you may be told that TSH levels of 1 to 2 mU/L are "fine" if you have mild hypothyroidism, it is possible to still have symptoms, especially if your levels tend to fluctuate.

Consider Other Levothyroxine Brands

Levothyroxine is the generic name of the drug marketed under many different brand names. The majority of people first starting treatment will be prescribed the Synthroid brand. Other available brands include Levoxyl, Levothroid, and Unithroid.

While the Food and Drug Administration (FDA) tightly regulates the type, purity, and amount of key active and inactive ingredients in a drug, different manufacturers (particularly generics manufacturers) may use different fillers and binding ingredients, some of which may affect drug absorption or trigger adverse symptoms.

Changing brands may potentially alleviate unintended side effects. Talk to your healthcare provider about whether this might be right for you.

Inquire About DTE or a T3 Drug

There are many healthcare providers who consider the addition of a T3 hormone, in the form of Cytomel (liothyronine or LT3), wholly unnecessary and problematic. They will point to the fact that it is prone to rapid uptake in the intestines and may quickly turn a hypothyroid problem into a hyperthyroid problem.

T3 hormones can also interfere with T4 blood test results and complicate the monitoring of your disease. All of these things are true but to a degree. The combination of Cytomel and levothyroxine may improve symptoms without any additional side effects compared to levothyroxine alone.

You may also consider dessicated thyroid extract (DTE) for symptoms of hypothyroidism. A study of 75 people who still experienced symptoms despite normal TSH levels found that adding LT3, or replacing it with DTE, did offer benefits for those most affected by their symptoms.

Keep in mind that medication may not be needed. One study identified LT4 use for subclinical hypothyroidism as one of four commonly overprescribed medications, especially in older adults.

Other Conditions Causing Hypothyroidism Symptoms

Several conditions can cause symptoms that are similar to those of hypothyroidism. They include:

TSH Low, T3 and T4 Are Normal

Low TSH and normal T3 and T4 can indicate subclinical (mild) hyperthyroidism. This has a number of potential causes, including pregnancy, Graves' disease, an enlarged thyroid (goiter) with multiple nodules, thyroiditis, and thyroid adenoma. TSH-suppressive therapy can also be to blame.

Summary

The American Association of Clinical Endocrinologists (AACE) and American Thyroid Association (ATA) provide hypothyroidism treatment guidelines for healthcare providers. It can help to discuss these options if you have normal TSH levels but still experience hypothyroidism symptoms.

The reasons for your symptoms may vary, depending on the underlying cause. Medication may not always be necessary but LT4 and other treatments may bring symptom relief. Consider alternative options, too, when talking with your endocrinologist. If you are uncertain about the care you are receiving, do not hesitate to seek a second opinion.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Mary Shomon
Mary Shomon is a writer and hormonal health and thyroid advocate. She is the author of "The Thyroid Diet Revolution."