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What causes Thyroid problems?

What Causes Thyroid Problems?

According to recent estimates, about 10 million Americans suffer from an under-active thyroid. This condition, called hypothyroidism, causes several tell-tale symptoms, including fatigue, brain fog, hair loss, constipation, low mood, and temperature intolerance. What causes low thyroid? These symptoms are related to inadequate or imbalanced thyroid hormones, including high reverse T3.

Diagnosing hypothyroidism is difficult without the experience of a medical professional as many of the symptoms are also common indications of other illnesses. 

I Dr. Terri Fox of Boulder Holistic Functional Medicine in Boulder, CO – recommend checking a full thyroid panel and a functional medicine approach to help you diagnose and address thyroid imbalances. Keep reading to learn more about hypothyroidism including why your reverse T3 levels are high and how to get tested.

The Dysfunctional Thyroid

The thyroid is a large butterfly-shaped gland in your neck. As part of the endocrine system, the thyroid is responsible for secreting certain hormones to regulate your metabolism, energy, reproduction, growth, and responses to injury, stress, and emotional state. 

The hormones made by the thyroid gland are mostly thyroxine (T4) and a little triiodothyronine (T3).

The secretion of thyroid hormones begins in the pituitary gland – often referred to as the master gland. Your pituitary gland makes the thyroid stimulating hormone (TSH) that tells the thyroid when to make more T3 and T4. 

When T3 and T4 levels are low, the pituitary gland produces more TSH, and the cycle continues.


T3 is the active form of thyroid hormone which influences the many bodily systems controlled by the thyroid. When T4 is released into the tissues and cells, ideally the body converts it into T3.

Sometimes, the cycle is interrupted and your body no longer creates T3. Instead, it produces reverse T3.

Thyroid Graphic 2

The absence of T3 in the body will trigger more TSH and more T4, but if the problem is not addressed, the system will continue to create more reverse T3. 

Reverse T3 is a competitive antagonist to free T3. Elevated reverse T3 blocks thyroid function, creating the same low thyroid symptoms, such as fatigue and weight gain. You can have normal free T4, free T3, and TSH levels but have elevated reverse T3 which leaves you functionally hypothyroid. Without a full thyroid panel, critical thyroid dysfunction might be missed.

Many conventional medicine doctors will prescribe T4 for people with thyroid disorders. But you can see that adding only T4 does not address the cause and, in many cases, only exacerbates the problem.

Factors That Cause High Reverse T3 Levels

1. Mineral Deficiencies (iron, zinc, iodine, selenium)

Your body is made of minerals, many of which are only available in your diet. However, soil depletion due to modern agricultural farming methods has made food less nutritious than it was in the past. 

Supplementation is becoming more and more necessary to ensure you have all of the vitamins and minerals you need. Some of the crucial minerals for thyroid function include iron, zinc, selenium, iodine, vitamin D, ferritin, vitamin B12, vitamin E, and vitamin A.

2. Adrenal Dysfunction

The adrenals are two glands found on the top of the kidneys. Like the thyroid, the adrenals are a part of the endocrine system, responsible for secreting hormones into the body. 

The thyroid and adrenals work synergistically to supply the body with hormones. A hypoactive thyroid strains the adrenals and vice versa. In functional medicine, we test the adrenals to see what role they might be playing in the health and function of your thyroid.

3. Mold Toxicity

People who have been exposed to mold are much more likely to develop issues with their thyroid. Mold dysregulates the immune system, interrupting communication between the cells. It creates undue stress in the body which can lead to hypothyroidism and elevated reverse T3. 

Mold is one of the top environmental triggers for thyroid problems that will also exacerbate current conditions. However, many everyday products contain harmful substances that severely affect the function of your thyroid including some plastic bottles and containers, detergents, food, toys, cosmetics, and pesticides.

4. Illness and Infection

Chronic illness and infection are other risk factors for thyroid dysfunction. These serious and prolonged problems cause stress to every organ system in the body, including the endocrine system. A compromised endocrine system eventually leads to insufficient levels of thyroid, adrenal, and sex hormones.

Thyroid Testing & Why It’s Important

A full thyroid panel is crucial to determine your course of treatment. For your panel, you need to make sure you get free T4 and T3 levels, instead of total thyroid hormone levels. Free T4 and T3 levels indicate the thyroid hormones that are unbound and able to enter and affect the body’s tissues. 

A full panel should include:

  • Free T3 and T4
  • Reverse T3
  • TSH levels
  • Thyroid antibody levels

All of these levels reveal something about the overall health of your thyroid. Low levels of free T3 or free T4 indicate hypothyroidism while high levels might suggest hyperthyroidism (overactive thyroid). TPO antibodies indicate Hashimotos, an auto-immune thyroid disorder.

If you are feeling any symptoms of thyroid dysfunction, your functional medicine doctor can help you interpret the results of your test to see if your thyroid is indeed contributing to your health woes.

Natural Treatments For Thyroid Dysfunction

Conventional medicine doctors often prescribe T4 for patients with symptoms of thyroid dysfunction. However, adding T4 to the body does not fix high reverse T3 or address whatever is causing the imbalance. Sometimes you need to stop taking T4 and take T3 by itself in order to reverse thyroid dysfunction. 

I also recommend supplementing with a bovine or porcine glandular supplement that contains both T3 and T4. These supplements are made from the glands of a pig or cow and contain enzymes and hormones that your thyroid needs to function. You may also take a T3/T4 pharmaceutical.

People with Hashimoto’s disease require a specific course of treatment. Too much iodine is harmful to people with Hashimoto’s since it can damage the thyroid or increase hypothyroid symptoms. I recommend supplementing with selenium which may help reduce thyroid antibodies.

Hashimoto’s disease is also exacerbated by gluten. Gluten may trigger thyroid dysfunction and contributes to gut dysbiosis which can lead to autoimmune disorders like Hashimotos. Eating a gluten-free diet is associated with lower thyroid antibody levels and reduces overall inflammation.

 Schedule An Appointment With Boulder Holistic Today!

Boulder Holistic is a functional medicine practice in Boulder, CO, that uses integrative medicine to address hypothyroidism. They search out the root cause of your unique symptoms to address – not only your physical health – but your emotional and mental health as well. 

Contact our office to schedule an appointment or ask any questions about what Boulder Holistic can do for you!

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Dr. Terri Rebibo Fox

Dr. Terri Fox is a holistic, integrative, functional medicine doctor in Boulder, Colorado. She works on your behalf as a medical detective searching for the underlying dysfunction, instead of just treating your symptoms. She has expertise in fatigue, bio-identical hormones, sleep disorders, gastro-intestinal dysfunction, and Chronic Inflammatory Response Syndrome from mold toxicity and Lyme disease.