The Thyroid: How It Works and What Can Go Wrong

8 Minute Read

Thyroid hormones are important for EVERY cell in your body to function properly. The thyroid regulates your metabolic rate, which means it controls your metabolism! Most of us think about weight gain/loss when we hear the word metabolism. Your metabolism is all of the chemical reactions that occur in your cells, including your VERY important energy systems! Metabolic dysfunction leads to the inefficient burning of fat. However, your thyroid affects so many other areas of the body, including heart rate, respiratory rate, body temperature, muscle strength, cholesterol levels, and so much more!

Thyroid hormones are made by the thyroid gland located in your neck and will affect all cells and organs in your body. Let’s look at HOW your thyroid should function so that we can understand what happens when you have thyroid disease.

Your brain is the first to signal to make thyroid hormones - your hypothalamus sends a signal to your pituitary gland (both in the brain) to send out Thyroid Stimulating Hormone (or TSH). TSH is essentially the signal telling the thyroid gland to make thyroid hormones.

TSH travels through the bloodstream to the thyroid gland, telling it to make the thyroid hormone called T4.

T4 is an INACTIVE form of thyroid hormones - meaning it needs to be activated before it can have any effects on the cell’s function.

T4 is activated into T3 - this is the hormone that actually has all of the effects controlling the functions listed above!

For my science nerds out there - the difference between T4 is and T3 is the number of iodine molecules incorporated into the hormone structure. Four iodine molecules in T4 and 3 iodine molecules in T3.

T3 is the active hormone that enters your cells and connects to their receptor. The connection between the hormone and its receptor will result in all of the thyroid functions we discussed earlier.

Thyroid: Brain to Gland

Converting T4 to T3

T4 is the inactive form of the thyroid hormone that is produced by the thyroid gland. Your body MUST convert this T4 to T3 - T3 is the ACTIVE form.

So, what do you need for this conversion to occur efficiently? There are over 28 cofactors that are required for T4 to be converted to T3. One example of those cofactors is the mineral selenium - if you have a nutrient deficiency in selenium, you will have a very hard time making this conversion.

This is why I test my patients for these cofactors to make sure they aren’t missing something that is needed for conversion of T4 to T3.

Where does conversion happen in the body? The conversion of T4 to T3 happens primarily in your liver, so you also need a healthy liver for proper thyroid function. Your liver has numerous functions and can get very bogged down with an unhealthy lifestyle. A happy liver is necessary for T4 to T3 conversion!

What is reverse T3?

To throw another loop into how complicated the thyroid is - your body can convert T4 into reverse T3 (rT3) instead of active T3. rT3 can block the function of your active T3 by blocking the receptors that T3 needs to connect with in your cell.

So, instead of active T3 filling those receptors, rT3 does instead.

This inhibits thyroid receptors from doing their job as mentioned above, like controlling your metabolism, temperature control, hair and nail growth, heart rate, breathing rate, and muscle function.

So, when does your body make rT3 instead of T3? rT3 is produced when your body is very stressed. It is designed to protect your life during extreme stress, like starvation.

However, your body can be under stress from nutrient deficiencies, poor gut health, food sensitivities, infections, toxin exposure and chronic stress. Stressors are very detrimental to your thyroid health!

Reverse T3


It is estimated that 20 million people have thyroid disease and likely 60% of them don’t know they have a problem. The thyroid can be difficult to diagnose because symptoms can be so varied and conventional doctors aren’t running the right tests for diagnosis!

Thyroid disease can result in either hypo (low thyroid hormones) or hyper (high thyroid hormones). Hypothyroidism develops most often in cases of thyroid disease.

Hypothyroidism takes YEARS to develop, typically a decade. Although there isn’t a clear cause, studies suggest that triggers or root causes push a person into hypothyroidism.

Common symptoms of hypothyroidism are:

  • Fatigue
  • Weight gain
  • Hair loss
  • Brittle nails
  • Constipation
  • Feeling cold
  • Depression
  • Slow heart rate
  • Puffy face
  • Memory issues
  • Dry skin
  • Muscle aches and stiffness
  • Heavy or irregular periods
  • Joint pain/stiffness
What is Hashimoto’s thyroiditis?

You may have heard of Hashimoto’s disease if you are dealing with hypothyroidism. Hashimoto’s thyroiditis is an autoimmune disease that results in hypothyroidism. Most people that are hypothroid actually have Hashimoto’s. Often, doctor’s don’t run the right tests to determine if they have Hashimoto’s.

So, what is Hashimoto’s?

It’s an autoimmune condition, meaning your body develops an immune response against your own thyroid gland.

The cause of autoimmune diseases likely involves the interplay of several root causes, which is why testing and working with a functional doctor really can help patients feel much better!

Let’s talk about what those root causes are that can lead to hypothyroidism.

Hashimoto's Disease

Thyroid Disease Root Causes

Thyroid disease most often leads to hypothyroidism, which is often caused by an autoimmune condition (Hashimoto’s). Thyroid issues often have some kind of trigger or root cause that leads to decreased thyroid function, including:

Nutrient deficiencies - For example, selenium, iodine, vitamin A, iron, zinc, vitamin D, magnesium are all needed to support the thyroid.

Poor Diet - A nutrient poor diet including - inflammatory, packaged foods, poor fats, and highly refined sugars will all negatively affect your thyroid function. Poor diet also leads to poor gut health.

Leaky Gut - Autoimmune diseases often have a leaky gut component where the connections between your cells in the digestive tract are letting particles into the blood and tissues that shouldn't be there. Your immune system sees them and has a reaction.

Food Sensitivities - Food sensitivities are foods that your body is having some kind of reaction to - this can increase inflammation, especially in the gut.

Infections - Chronic infections can cause an overall inflammatory response in the body, leading to autoimmune responses. The thyroid gland can be a target of this immune response.

Toxin Exposure - Toxins have numerous ways they can block the thyroid. For example, they can mimic the thyroid hormone and attach to its receptor. This will entirely block thyroid function!

Chronic Stress - Stress negatively affects the body in so many ways by increasing inflammation. In the thyroid, stress can also cause an increase in reverse T3 production, which blocks the active T3 thyroid hormone from connecting with the thyroid hormone receptor in your cells.

Thyroid Symptoms and Root Causes

The Problem with Current Treatments

Conventional medicine will typically prescribe a synthetic T4 when you have been diagnosed with hypothyroidism. Why does this only mask the problem?

First, we know that T4 must be converted to T3 for thyroid hormones to do their job! So, if the problem is conversion of T4 to T3, more T4 isn’t the answer! This is why so many people taking T4 continue to have the same symptoms.

The other issue can be with reverse T3 (rT3). Let’s say you add more T4 via medication and it actually converts to T3 properly. If rT3 is blocking the receptors, the T3 can’t get in and do what your body needs it to do!

Adding more T4 to the equation may be necessary, but it is hard to know without proper testing to figure out the ROOT cause of your hypothyroidism!!!

What Can You Do?

Your best course of action is to work with a functional medicine doctor to get the right testing so figure out what the root causes are of your thyroid disease.

Testing to figure out what root cause(s) you are dealing with help figure out how to make you FEEL BETTER! So much can go wrong with the thyroid as it is a complicated gland and process! It’s always better to test to figure out what is the root cause of hypothyroidism.

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