What Are Considered Normal Thyroid Hormone Levels?

Your thyroid gland is an essential part of your endocrine system. It secretes hormones that regulate metabolism, heart function, digestion, muscles, brain development, and bone health.

As functional healthcare providers, we test for levels of thyroid hormones beyond just TSH. Comprehensive thyroid hormone testing allows us to identify the root cause of many thyroid problems, not just the most severe cases.

In this article, we’ll talk about typical thyroid hormone levels, important thyroid tests, and what to do if you have hypothyroidism.

What Are Thyroid Hormones?

Thyroid hormones are secreted by the thyroid gland — the butterfly-shaped gland at the base of your neck. 

There are 3 thyroid hormones, but T4 and T3 are the most prominent. TSH, which is not actually made by the thyroid, is also a hormone vital to thyroid function, which is often what providers refer to when they mention “thyroid hormones.”

Here’s how TSH and thyroid hormones function within the body:

• T4 (thyroxine): The primary hormone produced by the thyroid gland. Also known as tetraiodothyronine, T4 is considered inactive. Its primary function is to become active T3.
• T3 (triiodothyronine): The active form of T4. It regulates your metabolism and other vital functions. Just 20% of T4 is produced in the thyroid. Most T3 is produced from T4 in other organs (like the kidneys and liver).
• Calcitonin: The less prominent hormone that your thyroid gland produces. It helps regulate calcium and phosphate levels in your blood, contributing to healthy bones.
• Thyroid-stimulating hormone (TSH): The production of thyroid hormone TSH occurs in the pituitary gland and stimulates the creation of T3 and T4. This is the hormone most often assessed for thyroid function.

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What is TSH and Why is it Important?

Thyroid-stimulating hormone, or TSH, might sound a bit like a mouthful, but it plays a crucial role in keeping your thyroid, and by extension, your entire body, running smoothly. Imagine TSH as the project’s manager, ensuring everything is on track. It’s produced by your pituitary gland, a small but mighty gland located at the base of your brain.

TSH’s main job is to regulate the production of T3 and T4 hormones by sending signals to your thyroid gland. Here’s how it works: when your pituitary gland senses that your levels of T3 and T4 are too low, it sends out TSH to nudge the thyroid into action, prompting it to produce and release more of these hormones.

On the other hand, if there’s too much T3 and T4 floating around, the pituitary gland will cut back on TSH production, telling the thyroid to ease up.

This feedback loop is vital because T3 and T4 are crucial for regulating metabolism, heart rate, and other critical bodily functions. When this delicate balance is disrupted, it can lead to thyroid disorders, such as hypothyroidism (low hormone levels) or hyperthyroidism (high hormone levels).

That’s why TSH is one of the first things doctors check when they suspect a thyroid issue. It serves as a reliable marker to determine whether further testing or treatment is necessary.

How We Assess Thyroid Hormone Levels

Many conventional primary care doctors and endocrinologists focus primarily on TSH levels. As functional healthcare providers, we administer a more robust set of thyroid function tests than most of the medical community.

Additionally, it’s important to consider optimal levels versus reference ranges. That’s why we administer a more thorough panel of tests to hypothyroid patients.

It’s important to remember that if you’re taking thyroid medications, the time from your last dose will change how we interpret your lab values. Your provider may have you test your thyroid panel before or after taking your medication in the morning to assess your thyroid levels at various times during the day.

We believe the most accurate and thorough way to test for thyroid function is to measure

• TSH levels: This test assesses whether your pituitary gland is producing too much TSH in response to low thyroid hormone levels or vice versa.
• Free T4: This test measures the amount of inactive T4 that’s converted into active T3. Low free T4 can indicate hypothyroidism, while high levels may be a sign of hyperthyroidism.
• Free T3: This test reads the level of active T3 in your blood. It helps determine how well your body is converting inactive T4 into active hormones.
• Total T4: This test measures both active and inactive T4 levels.
• Total T3: This test measures both active and inactive T3 levels, which is vital in assessing thyroid function.
• Reverse T3: This test measures the amount of inactive reverse T3, which can indicate a slowed metabolism and potentially point to thyroid issues.
• Anti-thyroglobulin and anti-TPO antibodies (Hashimoto’s thyroid antibodies): These other thyroid tests measure for autoimmune thyroid conditions, such as Hashimoto’s or Graves’ disease.
• Thyroid-binding globulin (TBG levels): This test measures the protein that binds to thyroid hormones and carries them through your bloodstream.

Important: Make sure you’re not taking biotin (vitamin B7) when testing for thyroid hormone levels. This popular supplement for hair and nail growth can interfere with test results.

What Is a Normal TSH Level?

So, what is a normal TSH level?

Optimal TSH hormone levels are 0.5-5.0 mIU/L, according to the mainstream medical community. But based on the best available research, we recommend 0.5-2.5 mIU/L — especially for pregnant women — for optimal thyroid function.

Pregnancy tends to reduce TSH values. You may dip below 0.5 mIU/L but remain euthyroid (which means your thyroid is healthy). Thyroid hormone levels may rise with each trimester, and then spike postpartum, but this is perfectly normal in the short term.

TSH Test

Testing levels of TSH is a common and critical part of any health practitioner diagnosing thyroid disorders. A blood test is the typical way to assess TSH levels.

The American Thyroid Association recommends serum TSH levels stay at 0.4-4.0 mIU/L (milli-international units per liter). We recommend keeping that number even lower — below 2.5 mIU/L.

However, we recommend keeping TSH levels between 0.5 and  2.5 mIU/L. If your TSH levels are too high, you may be hypothyroid. If your thyroid levels are too low, you may be hyperthyroid.

Certain medications might interfere with TSH measurements, like:

• Amiodarone
• Dopamine
• Lithium
• Potassium iodide
• Steroids like prednisone

What are normal TSH test results for thyroid levels? 

The normal range of thyroid test results is 0.5-5.0 mIU/L, but we recommend TSH levels stay under 2.5 mIU/L. If your TSH level sits outside this reference range, you probably suffer from a thyroid disorder that needs to be treated.

What is a normal TSH level in a woman? 

An optimal TSH level in a woman is 0.4-2.5 mIU/L. For pregnant women, that upper limit is stricter than if you are not pregnant.

A dangerously high level of TSH is above 10.0 mIU/L. High TSH means low thyroid hormones. This could indicate severe hypothyroidism.

What is considered a low thyroid level? 

A TSH level below 0.4 is very low, possibly indicative of hyperthyroidism (an overactive thyroid).

What is Considered a Dangerously High TSH Level?

Now that you understand the normal range of TSH levels, you may be wondering, “What is considered a dangerously high TSH level?”

A TSH level above 10.0 mIU/L is typically considered dangerously high and can indicate severe hypothyroidism. Symptoms of high TSH levels may include fatigue, weight gain, dry skin, hair loss, and more.

If you have a dangerously high TSH level, your doctor will likely recommend treatment to bring your thyroid levels back into the normal range. This could include thyroid hormone medication or dietary changes to support your thyroid function.

High vs. Low TSH

High TSH levels mean that you have primary hypothyroidism or subclinical hypothyroidism. Low TSH levels either mean that the pituitary gland is not functioning and you could have secondary hypothyroidism, or that you have hyperthyroidism (most likely from Grave’s disease).

Neither high nor low TSH is less of a problem than the other; both need to be addressed.

There are two main forms of hypothyroidism (an underactive thyroid):

1. Primary hypothyroidism: Primary hypothyroidism is when your thyroid itself is the reason your body isn’t making enough thyroid hormone. There’s not another part of your body triggering thyroid dysfunction.
2. Secondary hypothyroidism: If you produce too little TSH, you could suffer from secondary hypothyroidism, which means your thyroid disorder is caused by dysfunction wit the pituitary gland.

Another form of secondary hypothyroidism, or tertiary hypothyroidism, occurs when your hypothalamus releases too little thyrotropin. This issue with the hypothalamus can affect the pituitary gland, which in turn affects the thyroid gland.

What may be causing high TSH? Autoimmune diseases such as Hashimoto’s, toxin exposure, or even food allergies may be causing high TSH levels, which is due to low thyroid hormone levels and hypothyroidism.

What may be causing low TSH? Common causes of low TSH levels include:

• Autoimmune diseases
• Thyroid nodules
• Inflammation
• Inactive or underactive pituitary or hypothalamus glands
• Medication side effects

T4 Levels

Testing free T4 levels is standard practice for some medical practitioners. We also test total T4 for a complete picture. Both of these are blood tests. 

Our goal during treatment is to optimize our patient’s thyroid hormone levels to be in the middle-to-upper end of these thyroid hormone ranges (for free and total T4 and T3).

Typical T4 levels should be:

• Total T4 = 0.4-2.5 mIU/L or 5,000-12,000 ng/dL (nanograms per deciliter of blood)
• Free T4 = 0.9-1.9 ng/dL

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T3 Levels

Many healthcare professionals don’t test for T3 levels and rely primarily on TSH and T4 tests. We believe testing T3 levels is crucial to understanding a fuller picture of your thyroid function.

We test the following T3 levels: total T3, free T3, and reverse T3. These all can be measured via a blood test.

Typical T3 levels should be:

• Total T3 = 75-195 ng/dL (nanograms per deciliter of blood)
• Free T3 = 2.3 – 4.2  pg/dL
• Reverse T3 = 10-24 ng/dL
• Optimal reverse T3 levels would be around 15. Higher values are indicative of inflammation or stress (mental or physical).

T3 (triiodothyronine) impacts heart rate and the way your heart functions.

Symptoms of a Thyroid Issue

Hyperthyroidism and hypothyroidism are thyroid diseases caused by unbalanced thyroid levels. Thyroid replacement therapy often treats the following symptoms without actually addressing the root issue that’s causing the disease in the first place.

Thyroid disease symptoms include:

• Enlarged thyroid (goiter)
• Exhaustion
• Weight gain or weight loss
• Muscle and joint pain
• Dry skin
• Thinning hair or nails
• Temperature intolerance
• Digestive problems
• Depression and other mood disorders
• Irregular heartbeat
• Swelling
• Eye problems

Graves’ disease (hyperthyroidism) or Hashimoto’s thyroiditis (hypothyroidism) can lead to dangerously high or dangerously low thyroid hormone levels, respectively. There are many triggers for Graves’ or Hashimoto’s.

Treatment Options for Abnormal TSH Levels

Dealing with abnormal TSH levels might sound daunting, but there are plenty of effective strategies to help manage them. Let’s break it down for both high and low TSH levels.

High TSH Levels

Experiencing high TSH levels means your thyroid isn’t producing enough hormones, leading to hypothyroidism. Here’s what you can do:

• Thyroid Hormone Replacement Therapy: This is the go-to treatment. Your doctor will prescribe synthetic thyroid hormones such as levothyroxine to boost your thyroid levels back to normal. It’s like giving your thyroid a little helping hand.
• Lifestyle Changes: Incorporating a balanced diet, regular exercise, and stress management techniques can significantly improve thyroid health. Your thyroid loves a healthy lifestyle!
• Addressing Underlying Causes: Sometimes, high TSH is due to autoimmune conditions like Hashimoto’s thyroiditis. Treating the root cause is crucial, and it might involve working closely with healthcare providers to manage autoimmune disorders.

Low TSH Levels

Low TSH levels can be a sign of hyperthyroidism, where your thyroid is too active. Here’s how to handle it:

• Antithyroid Medications: These medicines help reduce the production of thyroid hormones, keeping everything in check.
• Radioactive Iodine: It might sound intense, but this treatment effectively reduces thyroid hormone production by shrinking the thyroid gland.
• Surgery: In severe cases, removal of part or all of the thyroid gland might be necessary. Don’t worry; your doctor will only suggest this if it’s the best option.
• Beta-Blockers: These don’t affect thyroid levels directly but can provide relief from symptoms like rapid heart rate and anxiety caused by hyperthyroidism.

Lifestyle and Dietary Recommendations

Managing your thyroid levels isn’t just about medication; lifestyle and diet play a pivotal role too.

1. Nutrition: Eating a diet rich in fruits, vegetables, whole grains, and lean proteins can support thyroid health. Selenium, zinc, and iodine are especially important nutrients for thyroid function.
2. Stress Management: Chronic stress can wreak havoc on your thyroid. Practices like yoga, meditation, and regular physical activity can help keep stress in check.
3. Regular Monitoring: Regularly checking your thyroid levels ensures you manage any changes promptly and effectively.

Combining medical treatments with a healthy lifestyle allows you to take charge of your thyroid health and live your best life. Remember, consistency is key, and small, mindful changes can lead to significant improvements.

The Role of Functional Medicine in Thyroid Health

Functional medicine takes a unique approach to thyroid health, totally different from conventional medicine. Rather than just treating symptoms, it digs deep to uncover the root causes of thyroid issues.

One of the coolest things about functional medicine is its emphasis on personalized treatment plans. No two patients are the same, so why should their treatments be?

Functional medicine practitioners for thyroid conditions such as our team at PrimeHealth Denver create customized plans that suit your individual needs, lifestyle, and biology. Depending on the case, we may suggest specific dietary changes, supplements, stress management techniques, or even particular forms of exercise tailored to you.

By focusing on the big picture, functional medicine aims to restore balance and improve overall well-being, not just mask symptoms with a one-size-fits-all prescription.

Many thyroid diseases can be permanently reversed. Even what conventional endocrinology specialists might call “permanent hypothyroidism” may be treatable. If you’re in Colorado, we’d love to help you find your cure.

When Is Treatment Needed?

Treatment is needed when your thyroid levels are too high or too low, ranging outside the optimal levels. Normal TSH levels are typically considered 0.5-5.0 mIU/L. We prefer the upper limit to be 2.5 mIU/L.

Thyroid hormone replacement using levothyroxine is the most common treatment for an underactive thyroid (too little thyroid hormone). Usually, thyroid medications like levothyroxine are not our first response to treating thyroid dysfunction.

Radioactive iodine, antithyroid agents, and beta-blockers are the most common treatments for an overactive thyroid.

There are many different root causes of thyroid conditions. The best treatment for either hypothyroidism or hyperthyroidism is addressing your unique root cause, such as stress, leaky gut syndrome, toxin exposure, nutrient deficiencies, inflammatory diet, or thyroid cancer.

Here at PrimeHealth, we do just that — create individual, integrative treatments that impact the root cause of your thyroid levels.

FAQs

Thyroid questions? Let us answer them.

Now you know all about normal thyroid hormone levels and when to seek help from a healthcare provider.

PrimeHealth is devoted to answering people’s questions about medical conditions and autoimmune diseases like Hashimoto’s thyroiditis. We believe it’s important to make patients feel heard and educated on what is going on in their bodies.

Many thyroid diseases can be permanently reversed. Even what conventional endocrinology specialists might call “permanent hypothyroidism” may be treatable. If you’re in Colorado, we’d love to help you find your cure. 

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Sources

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3. Udovcic, M., Pena, R. H., Patham, B., Tabatabai, L., & Kansara, A. (2017). Hypothyroidism and the heart. Methodist DeBakey cardiovascular journal, 13(2), 55.
4. Delitala, A. P., Scuteri, A., & Doria, C. (2020). Thyroid hormone diseases and osteoporosis. Journal of clinical medicine, 9(4), 1034.