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What Is Reverse T3?

Each thyroid hormone plays a unique role in regulating your health.

With Yasmin Akhunji MD

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Your thyroid gland, which is located at the base of your neck, is one of the VIPs of your endocrine system. This small but mighty gland plays a leading role in your overall health, and can impact your weight, sexual function, digestion, mood, energy levels, bone growth, heart rate, temperature and more.

Your thyroid gland produces two main thyroid hormones, triiodothyronine (also known as T3) and thyroxine (also known as T4). According to Olivia Rose MD, “The 3 and 4 correspond to the number of iodine atoms attached to the hormones.”

If you have too little thyroid hormone, you may have hypothyroidism, and if you have too much thyroid hormone, you may have hyperthyroidism.

Key symptoms of a hyperthyroidism include:

  • Anxiety or nervousness
  • Hair loss
  • Weight loss
  • Irregular menstrual cycles
  • Shaking
  • Hyperactivity
  • Feeling hot

Key symptoms of a hypothyroidism include:

  • Fatigue
  • Weight gain
  • Constipation or other digestive issues
  • Dry skin and hair
  • Brain fog

It’s important to know that you may not have all (or even any!) of these symptoms if you do have a thyroid condition — and that’s because these conditions play out differently in everyone. Some thyroid conditions stem from autoimmune issues, while others do not.

Beyond hyperthyroidism or hypothyroidism, there are a number of other conditions that could cause the above symptoms, including:

Thorough testing is required to understand the root of any symptoms or issues, since thyroid hormones are very complex.

How your thyroid gland works

Your thyroid gland works closely with both your hypothalamus and pituitary gland, which is located at the base of your skull. When your hypothalamus releases something called thyrotropin-releasing hormone, it triggers the pituitary gland to then release what’s known as the thyroid stimulating hormone (TSH).

TSH’s role is to oversee the stimulation of T3 and T4. If T3 and T4 levels are too low, more TSH is released. If the levels are too high, less TSH will be released.

It’s possible to have too much TSH, which could indicate that your thyroid gland isn’t using it correctly in order to produce the right amount of T3 and T4. It’s also possible to have too little TSH, which might indicate that your thyroid gland is actually making too much hormone. In this case, thyroid hormones might work to suppress the production of TSH.

All of these hormones work in a delicate feedback loop. Thyroid hormone imbalances could originate in your thyroid gland, or they could stem from your pituitary gland or hypothalamus.

What is reverse T3?

You might hear the term ‘reverse T3’ come up as you learn more about your thyroid health. Here’s what you should know:

First, it’s important to understand that the body can only use T3, which is the active form of thyroid hormone. T4 is basically inactive within the body, according to Yasmin Akhunji MD, a board-certified endocrinologist from Paloma Health. It’s really used to store and transport T3 around the body to where it’s needed.

Your thyroid gland makes about 80 percent T4 and only 20 percent T3. As a result, T4 is converted into T3 within your body by enzymes called deiodinases. This is why people with hypothyroidism are often treated with synthetic T4, which is then converted within your body.

According to Dr. Rose, “Reverse T3 (rT3) is the metabolically inactive form of T3. Reverse T3 contains the same number of iodine molecules [as T3] but attached to different areas.”

Reverse T3 is made from T4, Dr. Rose explains. “The normal process of thyroid hormone synthesis is the formation of T3 from T4. However, T4 can also form reverse T3.”

Why is this a potential problem? Reverse T3 can bind to a cell in the same way T3 does, except when reverse T3 binds to it, nothing happens. When this happens, Dr. Rose explains, “reverse T3 and T3 will then compete for receptors' at the cellular level. Your body can start showing symptoms of hypothyroidism when not enough T3 is binding to your cells.”

In cases of chronic disease such as HIV or kidney disease, starvation or extreme dieting, bone marrow transplantation, or kidney disease, reverse T3 can become elevated.

Is there a test for reverse T3?

If you’re experiencing symptoms of a thyroid condition or you’re trying to balance your hormones, you’ll need to get a thorough picture of your thyroid health. For example, testing for reverse T3 alone may not be enough. In fact, many healthcare practitioners wouldn’t recommend it.

“Reverse T3 is a controversial test that not many doctors know how to interpret or know what to do if it is elevated, especially if it is tested as a stand-alone,” Dr. Rose says. “Therefore, it should always be interpreted with T4, T3, thyroid antibodies, and TSH — along with an assessment of the patient’s symptoms.”

How to balance your thyroid hormones

To rebalance your thyroid hormones, the first step is a referral to an endocrinologist. Next, schedule an appointment for a full thyroid panel. Your endocrinologist may also want to order an ultrasound or biopsy to get a fuller picture of your thyroid health.

If necessary, your endocrinologist will prescribe medications to help balance your thyroid hormones. They may include synthetic thyroid hormones or anti-thyroid medication.

The good news is that you can play an active role in your own thyroid health. “Balancing your thyroid and its outputs requires a holistic approach,” Dr. Rose says.

In addition to taking the correct prescribed medication when necessary, some people with thyroid conditions also find that it helps alleviate symptoms if they limit processed foods, added sugars and refined carbohydrates. Replacing non-nutritious food with nutrient-rich veggies, dark greens, lean proteins and healthy fats may also help you feel better.

Other dinner table tips? “Include foods that are rich in iodine, such as sea vegetables. Your thyroid gland requires the amino acid tryptophan as well as selenium, B12, and vitamin D to function correctly,” says Dr. Rose. Make sure that any supplements you’re taking don’t secretly include T3. Check with your doctor to make sure they are safe before taking any new supplements with a thyroid condition.

Beyond food, you’ll want to get a grip on your stress levels by supporting your HPT, or hypothalamus-pituitary-thyroid axis.

“The HPT axis is the communication pathway that exists between the brain and your thyroid gland,” says Dr. Rose. “This pathway can become disrupted during times of chronic stress. Therefore, stress management is also key to managing thyroid function. You can try talk therapy, deep breathing exercises, mindfulness, meditation, exercise and adaptogenic herbs such as ashwagandha and Siberian ginseng to until you find the right combination to help lower your stress levels.”

Lastly, you’ll want to get your movement on — just be sure to clear it with your doctor first, especially if you have hyperthyroidism, as your metabolism may already be revved up. If you have hypothyroidism, regular movement is key. Try low-impact workouts like walking, hiking, swimming or dancing to get started.

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What Is T3?