Thyroid Part 1: What is it and How does it Work?


Discussions about the thyroid are a hot topic these days, and for good reason. From books to newspaper articles to whole websites, lots of people are talking about thyroid troubles and giving their input about how to resolve it.

Honestly, this is good news because a lot of people have thyroid problems. On the other hand, thyroid dysfunction being a hot topic means that there is lots of inaccurate and/or incomplete information out there.

Admittedly, the thyroid and its interactions with other organs and glands in our bodies are incredibly complex. There’s no way for a single blog post  or even a short series to explain everything about it.

At the same time, the topic of hypothyroidism with or without Hashimoto’s disease comes up so often that it seems necessary for me to give you at least some basic information about how it works, how you can tell if you have a problem (both objectively and subjectively), and what your next steps should be if you suspect an issue.

I mean, thyroid issues are so common that the American Thyroid Association estimates that as many as one in every seven adults in the U.S. has a low functioning thyroid, and up to 60% of those are unaware of it!

If you have a thyroid problem or you suspect you do, I want you to know that there are many holistic, natural ways for you to heal your thyroid (presuming it hasn’t been ablated). With the right approach and commitment, you likely can prevent further problems and may be able to restore it to optimal function… which means less medicine and less symptoms!

Okay, let’s get started…

What is the thyroid and what does it do?

Your thyroid is a butterfly shaped gland that sits in the low part of your neck and wraps around the front of your trachea (aka, windpipe). This little gland is responsible for many functions throughout the body including:

  • Metabolic regulation which determines the rate at which fat and carbohydrates are used for energy and cellular oxygenation rates
  • Body temperature control
  • Regulating the production of protein
  • Helping with calcium balance in the blood
  • Influencing heart rate
  • Mood regulation
  • Influencing hormone balance, especially the steroid hormones like estrogen

How does the thyroid work?

The most important thing to know is that the thyroid is in the middle of a whole system, often called the HPAT Axis (Hypothalamus-Pituitary-Adrenal-Thyroid Axis). This system works as indicated in this diagram and the text that follows:


  • The hypothalamus releases hormones that tell the pituitary gland what to do — TRH and CRH. Your hypothalamus does a lot more than release just these two hormones, but these are the two we care about for this discussion.
  • In response to the messages from the the hypothalamus, the pituitary gland then releases hormones that tell the thyroid and adrenal glands what to do, via TSH and ACTH respectively. You will notice that this means your TSH level is measuring what the pituitary is telling the thyroid to do, not what the thyroid itself is doing.
  • The thyroid then releases a hormone called T4, which is an inactive hormone, and a little bit of the active hormone T3.
  • The T4 hormone is then converted to T3 or Reverse T3 in many parts of the body, but especially the liver, gut, skeletal muscles and brain.
  • Both T3 and Reverse T3 compete for binding at the cellular level, but only T3 is capable of eliciting the desired change in the cell. Reverse T3 just gets in the way and prevents T3 from triggering the necessary steps within the cell. This means that the more Reverse T3 you have, the less T3 will be able to do its job and you may feel like you don’t have enough thyroid hormone in your body, even if you do.
  • In addition to the thyroid pathway, the adrenals release cortisol when triggered by ACTH. Cortisol negatively impacts the release of TSH and T4, as well as the conversion of T4 to either T3 or Reverse T3. This is why it is the HPAT Axis because the two pathways are so intertwined.

Executive Summary: The thyroid does not have an impact within the body until the T3 hormone is received and put to use by the cell.

This means that: 1) the pituitary has to send the right message to the thyroid, 2) the thyroid has to release enough T4, 3) other parts of the body have to create plenty of T3 and not too much reverse T3, and 4) the cell has to receive the T3 and put it to use.

Now that I understand what it’s supposed to do, how do I know if my thyroid is functioning properly?

Unfortunately, there’s no easy response to this question! I know you’re shocked, since it seems like there’s never an easy answer to the question of what could be causing a chronic imbalance in our body. (Wouldn’t it be nice if all of our symptoms were like a broken arm… get an x-ray and a cast and you’ll be better in a few months!)

In the next blog post of this series, I tell you how you can figure out if your thyroid is over- or under-performing. For now, I’ll give you a hint that most of the time, when your doctor or endocrinologist is looking at thyroid function, he/she is only measuring your TSH and maybe your T4 (as noted by the stars in the graphic above). This is not nearly enough information to tell whether or not your thyroid is doing its job and the cells know it!

Let me know below if you have any questions or comments about how the thyroid works as you move on to the next piece of information about figuring out what you may need to do to feel better.


Image via StockSnap.

— Allen S. Optimal Thyroid Health. In IFMNT Level II. Webinar.
— Berndston K. Hypothyroidism. In onebodymind. Whitepaper.
— Evan J. An Integrative and Functional Nutrition Approach to Adrenal, Thyroid and Hormone Dysfunction. In IFNA Track 2. Webinar.

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