Thyroid Health 101


The thyroid is a seriously misunderstood gland. 

It has a major role in regulating metabolism, so it becomes the scapegoat many times when someone has a hard time losing weight.   

But your thyroid is much more than just a thing that sits in your body and is either working or not / on or off.  It's integrated into your body in a major way. In fact, we have thyroid receptor sites in every cell in our bodies.  

As you've probably guessed, thyroid can be a complicated topic. So today’s blog is here to simplify thyroid function, what you need to know, and how you can support the health of your thyroid.

What is the thyroid?

The thyroid gland is a butterfly-shaped gland that sits in the front of your neck, and it regulates metabolism in response to inputs like stress, activity, and energy availability (food intake and body fat).

Because the thyroid is the main metabolism regulator, if it isn’t healthy you're more likely to struggle with weight gain or loss that is difficult to control.

Your thyroid is always releasing a steady amount of thyroid hormone into the bloodstream. At times it senses it may need to increase output, like when you’re cold, growing, or pregnant. 

When the thyroid is healthy it regulates processes in our body like hormone balance, metabolism, and protein synthesis by producing triiodothyronine (T3) and thyroxine (T4).  

A region of your brain called the hypothalamus releases thyrotropin-releasing hormone (TRH), which tells the pituitary gland to release thyroid-stimulating hormone (TSH), which tells your thyroid how much T4 to produce.    

When T3 and T4 increase, BMR (basal metabolic rate) goes up.  When this happens the heart rate increases, liver and muscle glycogen is used quicker, heart rate is faster, and in children the organs and bones grow. 

Thyroid also indirectly controls testosterone production and ovarian function because the ovarian cells in women and the leydig cells in men also have thyroid receptor cells on them.   

T4 must be converted to T3 (our active thyroid hormone) by enzymatic action.  This happens in the liver and gut and can be influenced by cumulative stress.  Stress can come from any number of sources including lack of sleep, poor nutrition, overtraining, and more.  

Image: Precision Nutrition

If the allostatic load (total of all stressors) is too high, or you are taking certain medications, or have excessive inflammation, this can disrupt the conversion of T4 to T3, which can disrupt the production of testosterone or ovulation.   

Thyroid hormone production controls the amount of adenosine triphosphate (ATP) that is used as fuel. Thyroid hormone can increase or decrease the amount of fuel used based on the amount of output.  

Let’s take a look at two of the most common issues with thyroid health associated with the output of thyroid hormone... 

hypothyroidism and hyperthyroidism.


Hypothyroidism means you have an under-active thyroid. 

This condition affects about 5% of Americans (about 10 million people), and is more common in women.  About 1 in 8 women are affected by hypothyroidism. 

Some side effects of hypothyroidism include

↦ Weight gain 

↦ Feeling cold

↦ Slow digestion (constipation, bloating)

↦ Dry hair and skin 

↦ Slowed heart rate 

↦ Infertility

And a few of the most common causes of hypothyroidism:

↦ Hashimoto’s thyroiditis - This is an autoimmune condition where your immune system is overactive and attacks your thyroid, which causes it to lower it’s output. 

↦ Hyperthyroid treatment - Treating an overactive thyroid can permanently lower thyroid output, causing hypothyroidism. 

↦ Thyroid removal - If you have to have your entire thyroid gland removed, it will cause hypothyroidism. 

↦ Radiation

↦ Medication


Hyperthyroidism means you have an overactive thyroid. 

With hyperthyroidism you produce too much T4, T3, or both. 

Hyperthyroidism is much less common than hypothyroidism. 

Symptoms of hyperthyroidism include: 

↦ Swollen or enlarged thyroid 

↦ High heart rate 

↦ Unexplained weight loss 

↦ Muscle wasting and weakness 

↦ Anxiety 

↦ Hair loss 

↦ Restlessness 

↦ Difficulty sleeping 

Causes of hypothyroidism include:

↦ Thyroiditis (inflammation of the thyroid) 

↦ Grave’s disease 

↦ Too much iodine

how to keep your thyroid healthy

Keeping your thyroid happy and healthy will in turn keep your metabolic rate at a good level, help your organs function properly, keep skin and tissues healthy and put you in an ideal hormonal environment to lose fat and build muscle.


As mentioned above, allostatic load can affect conversion of T4 to T3, so keeping stress under control can optimize thyroid output. You can think of stress as draining or charging your battery.  

You can focus on decreasing the drain on your battery (decreasing stress inputs), or charging your battery (stress-relieving activity), or a combination of both. (To our knowledge, Sam Miller deserves credit for the concept of "drains & charges".)

Some examples of ways to charge your battery:

 ↦ Spend time in nature, it has been shown to lower cortisol (stress hormone) levels and can be very relaxing 

↦ Walk; make it a slow relaxed walk, not a power walk.  You can combine this with being in nature and go on a hike.  

↦ Speaking of going on a hike, if you can look at the horizon, that big panoramic view has also been shown to decrease cortisol (whereas looking at a screen seems to have the opposite effect) 

↦ Get a massage 

↦ Deep breathing (i.e. ujjayi breaths/belly breaths) 

↦ Reading or journaling

↦ Having sex 

Some examples of drains to try to decrease: 

↦ Financial worries 

↦ Poor relationship management (fighting with loved ones) 

↦ Divorce 

↦ Stimulant overuse 

↦ Overdoing intense exercise (“HIIT classes”, endurance exercise, excessive cardio) 

↦ A world-wide pandemic

Maybe you can’t do much about some of these, but you can increase your “battery charges” to help even things out, and you can add some things to reduce the load of the stressors.  

Some examples from Precision Nutrition we love from to share with online clients include: 

↦ Talk to a therapist

↦ Limit exposure to news 

↦ Timebox worrying 

↦ Work from home 1x a week 

↦ Ask for help 

↦ Outsource chores 

↦ Timebox social media 

↦ Set boundaries 

↦ Automate less important decisions 

↦ Consider breaking up with toxic chronic stressors 

(Check out PN's "Effects of Stress on the Body" here.)

Using some of these tactics can reduce your allostatic load, and decrease the risk of stress affecting the health of your thyroid.

HEALTHY THYROID KEY #2: Maintain A Healthy Diet

You can eat in a way that supports your thyroid health. 

Like any other gland, organ, or process in your body, it needs the right macro and micronutrients to thrive.  In some cases it can be hard to get enough of these in your diet, and you may consider supplementing.

Some nutrients that are especially important for thyroid health:

↦ Iodine - Iodine is a major building block of both T3 and T4. It isn’t produced by our bodies so it needs to be found in the diet. Many people who switch to a healthy whole-foods diet will also cut out regular salt in favor of sea-salt. This is a fine switch, but it also cuts out iodine. 

You may consider using regular iodized salt on occasion, or use an iodized sea salt or iodized himilayan salt, that way you’re not missing out on iodine.  Another good source of iodine is kelp and seaweed.  Most grocery stores have seaweed snacks that can supply a good amount of iodine. 

↦ Vitamin D - It’s hard to get enough sunshine if you live in a warm climate, let alone if you’re in a northern state or have to work inside.  If getting in the sun for a long stretch of time daily (and in a tank top and shorts or shirtless) isn’t realistic, you may need to supplement with vitamin D.  

Vitamin D is a fat soluble vitamin, meaning it can accumulate, so it’s a good idea to get a blood test to see where you’re at before you supplement.  

Your daily supplement needs can vary widely from 1000 up to 10000 IUs to get your levels up to where they need to be.

↦ Magnesium - Most people are deficient in magnesium, so a daily magnesium supplement may be helpful. There are many forms of magnesium with varying levels of absorbability, so I recommend magnesium glycinate, or a combination of different forms of magnesium.  

In most instances if you go find magnesium in the grocery store it will be magnesium oxide, which doesn’t have very good absorbability so be aware of the type you’re picking up. 

↦ Zinc - Zinc can be found in meat, shellfish, nuts, seeds, and grains.  This one may be a little easier to get through food. Having enough zinc will not only keep your thyroid healthy but it’s very important for your immune system as well so make sure you’re getting enough. 

↦ Selenium - You can get enough selenium for the day from one brazil nut. It’s also found in fish and meat.

↦ Iron - You can find heme iron in red meat and liver, and non-heme iron in nuts, beans, spinach, and soy. Heme iron is more easily absorbed, so vegans may need to supplement.  

Women who menstruate may also need to supplement since they are bleeding monthly. Iron can be overdosed so be sure to have your blood levels checked to make sure you’re supplementing appropriately. (Also, calcium and tannins can inhibit iron absorption, so having dairy or tea can keep you from absorbing your iron. Vitamin C can enhance absorption so taking them together can help.) 

↦ Vitamin A - Sources of vitamin A include eggs, cod liver oil, orange and yellow produce, and green leafy vegetables. 

↦ Essential Fatty Acids - Unless you’re eating fatty fish a couple times per week you probably need to supplement. Look for a fish oil or cod liver oil (or algae oil for vegans) with >70% of total omega 3s as EPA and DHA.

HEALTHY THYROID KEY #3: Gut, Liver, and Kidney Health

Aside from maintaining an overall healthy diet, you need to make sure you have good gut health and good liver and kidney health.   

The liver and kidneys are sites for T4 to T3 conversion, and T3 sulfate and T3 acetic acid are converted to active T3 by gut bacteria. The good news is, maintaining good gut, liver, and kidney health requires the same principles as a  typical “healthy diet” recommendation.

[*Bonus:  eating this way and supporting your gut health will also benefit your immune system and help prevent the autoimmune condition Hashimoto’s that is the most common cause of hypothyroidism.]

A few ways to support your gut, liver, and kidney health:

↦ Drink plenty of water

↦ Don’t eat anything you have an immune response to 

↦ Eat plenty of whole foods and vegetables  

↦ Eat plenty of fiber; about 10-15g per 1000 calories in your diet 

↦ Avoid eating things that cause excessive bloating 

↦ Don’t eat past fullness 

↦ Avoid alcohol 

↦ Manage stress 

↦ Consider adding bone broth, L-glutamine, ginger, curcumin, and/or fermented foods  

↦ Exercise 3-6x/week

Getting your thyroid tested

If you have been having issues that cause concern about your thyroid function, you can go to your doctor and request a thyroid panel.   

Sometimes your doctor will be resistant to testing more than TSH because a lot of them like to look at just TSH and deduce any issues from just that value.  

The problem with that is you may have a healthy TSH level, but have a problem converting from T4 to T3, or are converting to reverse T3* (T3 not bound to a protein). You may also have normal TSH but have high thyroid antibodies which indicates Hashimoto’s thyroiditis. If you want a more in depth look you may have to specifically request more labs. 

[*Side Note: rT3 doesn’t carry out the metabolic processes T3 does.  When T4 converts to rT3 instead of T3, it’s usually because of starvation or illness, but some experts have suggested that chronic dieting may cause an increased conversion to rT3 in an effort to conserve energy, making subsequent diets harder.]

Common labs taken to assess thyroid health, along with their abbreviations and normal value ranges are:


While the thyroid is an important regulator of your metabolism, some portion of its health is within your control.  

There are ways to support your thyroid, lessen the likelihood of issues, and optimize your health.  And although some things that aren’t within your control can happen, there are medications to bring your thyroid into healthy function.

Improving your health with lifestyle, training, and good nutrition will help regardless of if you ultimately need medication or not. 

The same things that improve your body composition, gut health, organ function, digestion, and performance will support the health of your thyroid:  whole, unprocessed, nutrient-dense foods in the right proportions. 

If you need guidance getting your diet and training dialed in to optimize your health and body composition, click here now to chat with us about online coaching.

About The Author

Andrea Rogers is a certified nutrition coach, personal trainer, and coach for BairFit. Follow her on Instagram for more helpful training & nutrition content.

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