Overview of the Thyroid
Talk about an amazing gland. For something so small, symptoms of thyroid problems can have an impact on pretty much everything you do. I’m sure you’re aware that it is located in the neck and consists of two separate lobes.
Not to be confused with the parathyroid glands, which are named just because they are to the side of the thyroid (hence the prefix “para”) and do not share any of the functions of the thyroid gland.
Pretty much every cell in your body has a receptor to thyroid hormone. This means that it plays a role in the function of all of these cells. In some cases the effect is small, in others it is critical. As an example, thyroid hormone plays a critical role in human development (which is beyond the scope of this article—although mom’s thyroid hormone levels in pregnancy is critical to healthy development in the womb).
There are some cell types where thyroid hormone has very important roles. Most notably the hypothalamus / anterior pituitary, heart and skeletal muscle, kidneys and liver. When you look at these cells, you can begin to get an idea of just how much thyroid hormone can affect pretty much everything you do.
While the detailed list is extensive, the most commonly accepted functions of thyroid hormone include:
- Body temperature
- Body metabolism
- Muscle strength
- Appetite
- Heart rate and rhythm
- Liver function
- Kidney function
- Reproductive health
- Mood / brain function
- Gut function
The thyroid uses iodine to produce two main hormones: Triidothyrinine (T3) and thyroxine (T4). It all starts by adding iodine molecules to a protein called thyroglobulin. Add 3 total iodines and you get T3; add 4 and you get T4 (not too hard to figure out…).
T3, thyroxine, is about 3 to 4 times more potent on the body than T4.
But the thyroid gland produces way more T4 than T3. While this may seem a little backwards, the human body doesn’t do anything without a valid reason. It is produced this way because T3 is broken down way quicker in the body than is T4. In other words, if the thyroid produced T3 so it could be used by, say the pinky toe, it would never make it there before getting broken down.
So, in its brilliance, the body produces mainly T4 and converts it to T3 in the tissues where it is needed by an enzyme called deiodinase. There are 3 main types of this enzyme:
- Type I deiodinase is found mainly in the liver and kidney
- Type II deiodinase in skeletal muscle, the heart, fat, the thyroid itself and in the immune cells of the brain (astrocytes)
- Type III deiodinase in brain cells
This process, however, is prone to some problems. The activity of these enzymes is affected by quite a few factors:
- There is a daily (circadian) rhythm and a seasonal rhythm.
- The enzyme is dependent on the availability of selenium
- The beta blocker propranolol blocks this enzyme from working
- Lithium can speed up the enzyme activity
- Calorie restriction can slow down enzyme activity
- Stress and depression can slow down activity
- Prediabetes / insulin resistance will slow down activity
The list gets a lot longer, but you can begin to see that there are a lot of things that affect just how well the thyroid hormone that your body produces will work.
Interestingly, under stress, these enzymes will convert T4 into the inactive form of T3 called reverse T3, or just rT3. This means that, when you are stressed, you can take all of the Synthroid you want, it’s not going to get the job done (more on this later).
Trouble in Paradise; Symptoms of Thyroid Problems
The human body is an amazing machine. The way it works is beyond the grasp of pretty much everyone on the planet, although some of us have a slightly better understanding of how it works than others.
Everything functions with a brilliance that is truly beyond comprehension and explanation.
Except the thyroid. That can fall apart in your twenties and well…you just have to start on medications.
Wait…what??
Does this not sound ridiculous when put into the context of how every other system in our body works? What if your heart started to fail at 25 for no real reason? Your doctors would run every test imaginable to get to the bottom of the problem.
But not the thyroid. Maybe they’ll run some blood tests and do an ultrasound or two, but in the end doctors just kind of throw up our hands and hand out the prescriptions.
Many doctors are not aware of how vulnerable the thyroid is to insults from our immune system, toxins and our lifestyle choices, so there’s no way they can really help you.
Just what CAN go wrong with your thyroid?
Goiters
If you’ve ever flipped through the pages of National Geographic you’ve no doubt seen the sometimes disturbing images of just how bad a goiter can get. It’s that enlargement of the neck that will make even throwing on a 6 carat diamond pendent not quite enough to distract from the lumpiness smack dab in the middle of your neck.
Ninety percent of goiters are caused by iodine deficiency. Basically, consider your thyroid gland as an assembly line that can’t be shut off. Keep feeding in the raw materials, but leave out an important part (iodine). The product moving down the line can’t get finished because it’s missing the important part (iodine) so it just builds up and builds up, forming lumps.
That’s basically where an iodine deficiency goiter comes from and it’s pretty much an easy fix. Take iodine (more on this later).
While less common, autoimmune conditions can cause thyroid problems. Most notably of these are Hashimoto’s and Graves.
Hypothyroidism; Classic Symptoms of Thyroid Problems
This is what society seems to deal with most often. Even if it doesn’t start out this way, mainstream medicine has this fascination with wiping out the thyroid gland with radioactive iodine or surgery and leaving you with slow thyroid function anyway.
In hypothyroidism, for a variety of reasons, there is not enough thyroid hormone produced (both T3 and T4), leading to the classic symptoms of thyroid problems stemming from a slow thyroid.
- Constipation
- Fatigue
- Weight gain
- Depression
- High cholesterol
- Course or thinning hair, dry skin and brittle nails
- Cold intolerance
There are other items on the list, but these are the most recognizable.
Hashimoto’s disease is a very common condition causing these symptoms of thyroid problems, but this will be discussed shortly.
Hyperthyroidism; Too Much of a Good Thing
Ricochet rabbit. The Tasmanian Devil. The Road Runner. All classic examples of what happens when the thyroid gland goes haywire.
Which is pretty much the opposite of what happens with symptoms of thyroid problems from hypothyroidism. With a few exceptions that basically involve burning the candles at both ends. Things like bone loss, heart palpitations, muscle loss, insomnia are all on the list of problems created by too much thyroid activity.
Hyperthyroidism can be caused by many different things, but most common are situations in which the immune system is attacking portions of the thyroid pathway (auto-immune). When the immune system begins to attack the thyroid, the thyroid may respond by over-producing thyroid hormone, producing the list of symptoms we’ve just covered.
Hashimoto’s Autoimmune Thyroiditis
Named after the Japanese physician who first described the condition in 1912, Hashimoto’s thyroiditis happens when the immune system attacks various parts of the thyroid pathway. These can include:
- Thyroid peroxidase – the enzyme that is absolutely essential to prepare iodine to be put together to make T3 and T4 (oxidizes iodide to iodine)
- Thyroglobulin – the base protein that iodine is attached to in order to make T3 and T4
- TSH receptors – the receptors on the cell for thyroid stimulating hormone (TSH) made by the pituitary that will stimulate the thyroid to make T3 and T4
When the immune system attacks these proteins, it’s going to cause problems. Initially, the immune system attack may be subtle with no symptoms.
Over time, however, this process destroys the thyroid, leading to hypothyroidism.
Grave’s Autoimmune Thyroiditis
Wow. Does anyone besides me find it strange how many autoimmune conditions there are in the human body?? Pissing off your immune system enough to have it turn around and attack you is never a good thing, and the thyroid seem to be a central focus of this hostility.
Grave’s is the most common cause of hyperthyroidism in the human body, accounting for some 50-80% of cases of elevated thyroid hormone activity. Since it’s a hyperthyroid condition, you can imagine the symptoms—elevated heart rate, weight loss, insomnia, and so on. One thing that happens with Grave’s that is different, however, is the bulging eyes (exophthalmos) that is caused by increased fat tissue behind the eyeballs, pushing them outward.
Grave’s autoimmune thyroiditis is caused by the immune system attacking the thyroid stimulating hormone receptor (called thyroid stimulating immunoglobulin, or TSI). While the immune system may also attack thyroglobulin and thyroid hormone just like Hashimoto’s, but this is not as common.
Typical medical treatment is typical. Don’t find out what’s wrong—just nuke the thyroid with radioactive iodine, surgery or anti-thyroid drugs like methimazole. I’ll cover the problems with this approach a little later.
Thyroid Cancer
Regardless of the tissue that it shows up in, the “C” word scares everyone. Thyroid cancer is no exception. But before you lose any sleep over it, there are some facts you need to know.
There are two main types of thyroid cancer: papillary and follicular carcinoma. Papillary is by far the most common type of cancer found (75-85%)
I’m not going to go too much into this topic later, but later I’ll make sure I explain why the diagnosis of thyroid cancer is such a big mess in medicine today.
Signs of Thyroid Problems; Lab Tests and Imaging
You’re complaining of fatigue and constipation and your formerly full head of hair is now looking a little closer to mine. Your doctor will likely order some basic labs to get a better look at your thyroid, but you need to make sure that the right tests are ordered.
Most doctors will order just a TSH and be happy thinking that the results of your TSH will give him a good idea of what is going on with your thyroid (if anything). This is not even close to the truth.
Labs to Evaluate Symptoms of Thyroid Problems
Before I go into the various labs to evaluate your thyroid problems, there is something very important that needs to be said first.
There are labs and there are patients. These two don’t always match up on an individual basis. I have had patients who could check off pretty much every symptom on the hypothyroid list and yet labs are normal. Because of this his or her doctor loudly proclaims that the thyroid is normal, totally ignoring the patient’s symptoms staring at him or her slack-jawed.
On the other hand, I have had patients put on thyroid hormone based purely on labs when the patient has no symptoms.
When looking at normal lab values, this does not mean that these labs are normal for YOU. There is always some variation from person to person and your doctor needs to be aware of this.
Symptoms of Thyroid Problems: Thyroid Stimulating Hormone (TSH)
TSH is the classic lab test for thyroid function. It is done with pretty much every lab test panel that I have seen. Thyroid stimulating hormone is the hormone produced by the pituitary gland and runs through the bloodstream to stimulate the thyroid to start producing thyroid hormone.
This means that, if the thyroid gland is sluggish or not working at all, TSH levels will go up. Why? Because the pituitary starts working harder and harder to get the message to the thyroid gland to stop slacking off. The higher the TSH, the more lazy the thyroid gland is acting.
On the flip side, lower levels of TSH means that there is already enough thyroid hormone running through the blood and the pituitary wants the thyroid gland to back off on activity.
Thyrotrophin Releasing Hormone (TRH): Kicking it all off
The whole shebang starts with the master gland in the brain called the hypothalamus. It is the hypothalamus that truly decides whether or not there is enough thyroid hormone circulating in the bloodstream. Not enough thyroid hormone–the hypothalamus releases TRH and sends it next door to the pituitary gland to release TSH. And the reverse happens as well when too much thyroid hormone is present.
If your doctor thinks that the thyroid is working OK but maybe there is something wrong with the pituitary, he or she can order a TSH-stimulation test. In this test, TRH is injected directly into the blood and the amount of TSH produced as a result of giving the TRH is measured to get an idea of how well the pituitary is working.
Free T3 and Free T4
These are the classic version of testing thyroid hormones in the blood. The reason it is called “free” is because this test checks for thyroid hormone that is not attached to a carrier protein. When hormones are attached to proteins, they are generally in the inactive state. So, checking for protein-bound hormones is not really checking for the hormone in a state that our body can use. Hence the use of “free” T3 and T4.
Thyroxine Binding Globulin
This is the protein that thyroid hormone gets attached to in the blood. As mentioned, hormones attached to proteins are inactive. This means that, when levels of TBG go up, there is less free thyroid hormone to have an effect on the body. The most common situation that can drive up TBG levels is when estrogen levels go up (such as using hormone replacement therapy).
Reverse T3
Everything else on your labs seems to be normal, but you still feel like last month’s dinner hasn’t quite made it out of your colon yet and your previously-thick head of hair is now ready for a comb over just to keep your scalp from getting fried in the sun.
Things like stress can greatly affect your body’s ability to convert T4 into active T3—with high levels of cortisol (from stress), your liver will convert T4 into the mirror image form of T3, called reverse T3 (or just rT3 for short).
Thyroid Protein Antibodies
NO good lab testing for thyroid function is complete without looking for typical antibodies to proteins involved with normal thyroid activity. Every single one of us has some degree of autoimmunity to most tissues in our bodies; it’s just a matter of how strong the immune response is. The more pissed off your immune system is at how you’re treating it, the higher your levels of autoimmunity. This applies to all autoimmune conditions, regardless of whether we are talking about multiple sclerosis, rheumatoid arthritis, lupus or Hashimoto’s autoimmune thyroiditis.
I’ll go over how to calm down your body’s autoimmune reaction later in this article.
The three main autoimmune antibodies to look for when dealing with symptoms of thyroid problems are thyroid peroxidase (TPO) antibody, thyroglobulin (TG) antibody and thyroid stimulating hormone receptor (TSHR) antibodies.
Your doctor really can’t make a determination of what is causing the symptoms of your thyroid problems without a full evaluation of these autoimmune antibodies. Period. Despite this, it seems like most patients that I see were given a diagnosis of hypothyroidism based on TSH alone, with no idea about WHY there is a thyroid problem.
Ultrasound
After labs, the next go-to testing for the thyroid is an ultrasound of the thyroid. Your doctor will probably order this non-invasive test to get a closer evaluation of any nodules that he or she may have found on palpation. Ultrasound can also be used to guide a needle biopsy of the thyroid.
Ultrasound is generally a safe procedure that does not involve any ionizing radiation like there is with a CT scan or X-rays. However, as I wrote about extensively in Breast Cancer Myths, more information is not always a good thing. With mammography, there is a massive issue with overdiagnosis leading to overtreatment. The costs, in both dollars and quality of life, is practically incalculable.
Ultrasound for the thyroid is not too far off this same mark. But more on this later.
Advanced Imaging for Symptoms of Thyroid Problems: CT scan and MRI
Let’s just start this section off by saying that CT scanning is massively overused. Which wouldn’t be a problem if the radiation exposure from CT scans were not linked to some 29,000 cancer cases per year. MRI, on the other hand, does not expose you to any radiation.
In general, CT scans are much better for visualizing things immediately (like bleeding on the brain from trauma) and for imaging bone. Neither of these are really an issue with the thyroid, which makes MRI the imaging of choice for your thyroid.
But before you run off and cancel your thyroid CT scan in lieu of a MRI, make sure you finish this article.
Biopsy
This is a pretty self-explanatory option for taking the closest look at your thyroid to get a better idea of what may be causing that lump that you found in your thyroid. This is usually done as a fine-needle aspiration and is guided by ultrasound to make sure that the sample of tissue comes from the mass that was found.
This ends part 1 of this article. In part two, we’ll go much more into depth about where things go wrong with your thyroid, what causes thyroid problems and, most importantly, what to do about it.
Mike Noonan, DC says
Thanks for these articles, I find them a both a great review and an opportunity to learn something new. Who knew there was a test for thyroid antibodies? Well, now I do! Thanks
Plus it reinforces my frustration when so many patients are on thyroid meds for what see to me pretty scant evidence. After a while you start to think it’s you who is nuts….
James Bogash says
Dr. Noonan,
Thanks for the comment. I wanted to put this one into a single article, but realized there was just too much on the “why” portion of thyroid problems to keep it to a single long article. Stay tuned.
Dr. Bogash
Susan Germany says
Wooooowwww, Thank you for featuring this article on the Thyroid. I have a congenital hypothyroidism problem and thought I had a clear understanding of this condition. But you educated me on the t3 and t4 hormones which I didn’t truly understand before. How can I get a written hard copy of this article to refrence to in case I need I need it in the future?
Thank you again.
James Bogash says
Susan,
Thanks for the comment. Make sure you look for part 2–it goes a lot more into how to improve thyroid function. As for a written copy, the best way is just to print it out. But, considering that this article will remain on the website for eternity (or until the EMP blast), than you can always come back here to read it again and again.
Dr. Bogash