What is the thyroid gland?
The thyroid gland is a butterfly-shaped gland that sits in the base of the neck. It secretes thyroid hormones that control metabolism and many other critical functions in your body.
What are the thyroid hormones?
The thyroid hormones are the most important hormones in your body, affecting every physiological pathway. The two main thyroid hormones are:
- Triiodothyronine (T3): the active version that cells sense and utilize
- Thyroxine (T4): the precursor that’s used to make T3
The thyroid gland secretes about 10% T3 and 90% T4. Because the cells have receptors to T3 only, which means they can only ‘see’ T3, T4 must be converted to T3 before the cells will recognize it. The conversion of T4 to T3 happens in the liver, muscles, and the digestive tract. Thyroid symptoms can appear when your body can’t convert T4 to T3 properly.
Think of your thyroid gland as your car’s gas pedal. When cruising properly, you feel great, have energy, burn enough calories to maintain your weight, and so on. When it’s off, it feels like you have one foot on the gas and the other on the break pedal. You slow down, have ups and downs, and run out of steam.
Your body will work to keep the levels of T3 and T4 within a normal range all the time. Hypothyroidism is generally when you have low levels of T3 and/or T4, and hyperthyroidism is when you have high levels of T3 and/or T4.
Symptoms of Hypothyroidism (low thyroid hormones)
- Fatigue, tired, sluggish
- Weight gain despite eating a low-calorie diet
- Morning headaches that wear off as the day progresses
- Need for excessive hours of sleep to function well
- Constipation or difficult bowel movements
- Hypersensitivity to cold weather
- Poor circulation and numbness in hands and feet
- Cold hands and feet/feeling cold all over
- Low auxiliary body temperature, less than 98.6 first thing in the morning (may also be caused by any hormonal imbalance)
- Muscle cramps while at rest
- Increased susceptibility to colds and other viral or bacterial infections and difficulty recovering from them
- Slow wound healing
- Chronic digestive problems, such as lack of stomach acid (hypochlorhydria)
- Itchy, dry skin
- Dry or brittle hair
- Hair falls out easily (scalp, face, or genitals)
- Loss of outmost portion of the eyebrow
- Swelling, especially facial (myxedema)
Symptoms of Hyperthyroidism (elevated thyroid hormones)
- Heart palpitations
- Inward trembling
- Increased pulse rate, even at rest
- Feelings of nervousness and emotional distress
- Night sweats
- Involuntary weight loss
- Difficulty gaining weight
Normal Thyroid Hormones Levels
Before discussing what normal thyroid levels are, there are two other glands that you need to get to get familiar with—the hypothalamus and the pituitary. Both glands are located in the brain and communicate with the thyroid gland to maintain normal levels of T3 and T4. These three glands are often referred to as the HPT-axis (hypothalamus-pituitary-thyroid).
The hypothalamus and pituitary control the production of thyroid hormones from the thyroid gland. The hypothalamus produces a hormone called Thyroid Releasing Hormone (TRH) that communicates to the pituitary to release a hormone called Thyroid Stimulating hormone (TSH). The latter signals the thyroid to produce T4 and T3. When T3 and T4 levels are low, these two glands will stimulate the thyroid gland to produce more. If T3 and T4 levels are high, these glands will sense that, stop producing TRH and TSH, which will stop the production of thyroid hormones. The image helps explain the HPT-axis.
To properly assess your thyroid function, you need at minimum 3 different numbers: TSH, free T4, and free T3. Many internal and family doctors only check for TSH and assume that your thyroid labs are fine. However, this is not necessarily true all the time. You can have enough TSH but not enough T3 for your cells to use. There are many scenarios where TSH can be normal, yet thyroid function is subpar.
What is considered ‘normal’ thyroid levels from a functional medicine perspective is different from conventional medicine perspective. See the table for the different ranges. Because functional medicine focuses on optimal health—not just the absence of disease—and because it views the body as one whole system where many symptoms can be traced back to thyroid function, the functional medicine ranges tend to be tighter.
Reverse T3 (rT3) is another lab value that functional medicine considers. If you have too much T4, your body will convert the excess to rT3 to keep your T4 and T3 levels in balance. It’s normal to have some rT3, but because it is inactive and looks like T3, it will block your cells from using the active T3. Stress (physical, mental, emotional), infections, medications and uncontrolled diabetes increase the conversion of T4 to the inactive rT3. In these situations, your body wants to reserve energy so it produces less T3. On the outside, you feel slow, burn less calories, feel cold, make less hair, etc.
The remaining necessary labs are thyroid antibodies; anti TPO (Thyroid Peroxidase AB) and anti-thyroglobulin (Thyroglobulin AB). These antibodies are generally associated with autoimmune thyroiditis, also known as Hashimoto’s disease. In this condition, your immune cells attack your thyroid gland, reducing its ability to produce adequate thyroid hormones.
The most comprehensive and cost-effective test we use in our office is Spectracell’s complete thyroid labs panel. Click HERE for more information.
Factors that Contribute to Thyroid Problems
There are many factors that inhibit the production of thyroid hormones (T4 and T3) and the conversion of T4 to T3.
The thyroid gland needs iodine, iron, tyrosine, zinc, selenium, vitamin E, vitamin B2, vitamin B6, vitamin B12, vitamin C, and vitamin D to produce thyroid hormones. Deficiencies can result from eating a diet low in these nutrients, taking medications that deplete these nutrients, gut inflammation that results in reduced digestive enzymes to extract nutrients, gut dysbiosis which interferes with digestion and absorption, and long-term use of acid suppressing medications. We use the Micronutrient Deficiency test to custom-design a supplement and food-focused plan.
In times of stress, the body will produce more rT3 from T4 and less T3. That’s because the body is trying to conserve energy in times of danger. Stress can be an injury (like a car accident), surgery, acute infection like the flu, long-term like Lyme disease or gut dysbiosis, inflammation in any part of the body (especially in the gut where T4 to T3 conversion occurs), chronic exposure to cold weather, severe calorie restriction, or uncontrolled diabetes.
Gastrointestinal (gut) problems:
Improper digestion and absorption can trigger nutrient deficiencies that disturb proper thyroid function. But even if you have adequate nutrients, problems like gut dysbiosis, gut infections (candida, H Pylori, SIBO), and leaky gut are all sources of inflammation that raise costisol levels. High cortisol will reduce the conversation of T4 to T3 and increased the conversion of T4 to rT3. Gut dysbiosis will interfere with the activation of T3 since healthy gut bacteria produces an enzyme called intestinal sulfatase that is responsible for that. Constipation can reduce the amount of T4 and T3 available in the blood (low thyroid function also contributes to constipation, and it’s a cycle that needs to be broken). I often recommend a gut health stool test to assess gut dysbiosis, leaky gut, and other markers of gut inflammation.
The liver, which is part of the gastrointestinal system, converts T4 to T3. If the liver is congested, overworked, under a lot of toxic load, or unable to eliminate toxins, available T3 will be reduced. Proper detoxification through food and supplements that provide nutrients like vitamin C, NAC, alpha lipoic acid, and others is necessary. You can read more about my real food and medical detox program. for Sometimes, the liver produces more or less thyroid binding globulin (TBG), a protein that carries T3 in the blood, due to hormonal imbalances (estrogen and testosterone).
Food sensitivities are non-IgE immune reactions to food and food chemicals. Food sensitivities are linked to leaky gut, gut dysbiosis, lack of digestive capacity, nutrient deficiencies, and others. Symptoms of food sensitivities include digestive discomforts, headaches, migraines, brain fog, fatigue, skin issues, muscle pain, and more. Eating foods that trigger the immune system is a source of inflammation that will slow down your thyroid. More information about food sensitivities here.
Auto-immune activation (autoimmune thyroiditis):
A large number, about 90%, of hypothyroid cases are caused by the autoimmune condition Hashimoto’s. In Hashimoto’s, the cells of your immune system (lymphocytes) attack your own thyroid cell resulting in less T4 and T3 production. What triggers an autoimmune attack on the thyroid? Several things including a genetic predisposition, pre-existing auto-immune condition like celiac or type 1 diabetes, gluten sensitivity, gut infections (parasite, SIBO, candida), and nutrient depletion (especially zinc or glutamine that feed the intestinal lining).
(In some cases, the lymphocytes invading the thyroid can cause it to become so enlarged that you can visibly see a mass in the neck. This is called goiter. Consult with a physician who can screen for abnormal growth like cancers or infections).
Certain medications, like Propranolol (a beta blocker) or corticosteroids, can inhibit the conversion of T4 to T3.
Improve Thyroid Health with Diet
Since there are several things that contribute to to low thyroid function, the diet or nutrition therapy is going to change accordingly. The best plan for you needs to be individualized, and advanced tests often help map out what needs to be addressed first.