What Are Considered Normal Thyroid Hormone Levels?

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

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

What are thyroid hormones?

Thyroid hormones are secreted by the thyroid gland — the butterfly-shaped organ at the base of your neck. Three thyroid hormones exist, but T4 and T3 are the most prominent.

Here’s what each thyroid hormone does within the body:

  • T4 (thyroxine) is the primary hormone produced by the thyroid gland. Also known as tetraiodothyronine, T4 is inactive. Its primary function is to become active T3.
  • T3 (triiodothyronine) is the active form of T4. It regulates your metabolism and other vital functions. Just 20% is produced in the thyroid, while most T3 is made in other organs (like the kidneys and liver) from T4.
  • Calcitonin is the less prominent hormone that your thyroid gland produces. It helps regulate calcium and phosphate levels in your blood, contributing to healthy bones.

TSH And Its Role In Thyroid Function

TSH stands for Thyroid Stimulating Hormone. It’s the primary hormone checked by doctors to assess thyroid function. TSH is secreted in the brain by the pituitary gland, not the thyroid gland. 

The pituitary gland will secrete more TSH in response to sensing a need for more thyroid hormone production. TSH then travels to the thyroid gland (in the neck) and, as its name implies, stimulates it to make more thyroid hormone. TSH is one of your body’s natural defenses against hormone imbalance.

Symptoms Of A Thyroid Issue – Understanding Thyroid Levels

What are the symptoms of a thyroid problem? The symptoms of a thyroid problem comes from hyperthyroidism or hypothyroidism, both caused by unbalanced thyroid levels.

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

It’s crucial to know if a patient’s thyroid imbalance is due to Hashimoto’s or Grave’s disease — these are autoimmune conditions with a significantly different root cause and treatment strategy than thyroid disease — which is not autoimmune.

Optimal TSH Levels

Optimal TSH hormone levels are 0.5-5.0 mIU/L, according to the mainstream medical community. We recommend 0.5-2.5 mIU/L, though — especially for pregnant women.

Pregnancy tends to reduce TSH hormone levels. 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, then spike postpartum, but this is perfectly normal in the short term.

Thyroid hormone levels are measured with blood tests.

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 5.0 mIU/L. High TSH means low thyroid hormones. This could indicate severe hypothyroidism.

What is considered a low thyroid level? A TSH level of 4.5 mIU/L and above typically indicates hypothyroidism.

Testing For T3, T4, And TSH Thyroid Levels

Many conventional primary care doctors and endocrinologists focus primarily on TSH levels. Here at PrimeHealth, 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 range levels. 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
  • Free T4
  • Free T3
  • Total T4
  • Total T3
  • Reverse T3
  • Anti-thyroglobulin and anti-TPO antibodies (Hashimoto’s thyroid antibodies)
  • Thyroid-binding globulin (TBG levels)

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 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.

T4 Test

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 patients’ 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

T3 Test

A lot of healthcare professionals don’t test for T3 levels. 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).

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 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.

High Vs. Low TSH

Elevated TSH levels mean that you have primary hypothyroidism or subclinical hypothyroidism. The problem in primary hypothyroidism is that your thyroid gland is not producing enough thyroid hormone, so the pituitary gland is doing its job by trying to stimulate the thyroid with increased TSH levels.  

In subclinical hypothyroidism, the TSH is elevated, while the thyroid hormone levels are still in the normal reference range. 

Low TSH levels either means 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.

What does a high TSH mean?

What can happen if the TSH level is too high? If a TSH level is too high, it may be a sign of hypothyroidism. Here are some of the symptoms of hypothyroidism:

  • Enlarged thyroid (goiter)
  • Fatigue
  • Weight gain
  • Muscle and joint pain
  • Hoarse voice, snoring
  • Dry skin
  • Thinning hair
  • Brittle nails
  • Cold intolerance
  • Constipation
  • Depression
  • Heart disease
  • Myxedema coma

There are two main forms of hypothyroidism or an underactive thyroid:

  1. Primary hypothyroidism is when your thyroid is the problem. There’s not another part of your body triggering thyroid dysfunction.
  2. Thyroid-stimulating hormone (TSH) is not a thyroid hormone. TSH is produced in the pituitary gland, but it dramatically affects the thyroid. If you produce too little TSH, you could suffer from secondary hypothyroidism, which means your thyroid disorder is a pituitary problem.

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 does a low TSH mean?

A low TSH level means you either suffer from secondary hypothyroidism or hyperthyroidism. This means your thyroid gland is making too much thyroid hormone.

The symptoms of hyperthyroidism include:

  • Muscle weakness
  • Too much energy
  • Insomnia
  • Fatigue
  • Heat sensitivity
  • Diarrhea
  • Frequent urination
  • Thirst
  • Itchiness
  • Anxiety
  • Mood swings
  • Osteoporosis

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

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.

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 educate them on what is going on in their bodies.

Did you know — a lot of people’s hypothyroidism can be permanently cured. Even what conventional endocrinology specialists might call “permanent hypothyroidism” may be treatable. Our patients prove it.

To schedule a FREE phone consultation with a medical staff member, schedule your appointment today.

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  4. Udovcic, M., Pena, R. H., Patham, B., Tabatabai, L., & Kansara, A. (2017). Hypothyroidism and the heart. Methodist DeBakey cardiovascular journal, 13(2), 55.
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