What Does your Thyroid Do? 10 Critical Functions to Know

Call me biased, but I would tell you that your thyroid is the most important endocrine gland in your body.

Not only does it interact with almost every single cell, it also regulates and controls critical processes like your weight and cholesterol levels.

But we are putting the cart before the horse.

If you are like most people, then it can be confusing trying to learn about your thyroid.

But today, we are going to make it simple and I’m going to explain how your thyroid works so that anyone can understand:

Thyroid Gland Basics

Thyroid problems can seem complex when you first look at them but they don’t have to be. 

Your thyroid is a gland that sits at the base of your neck and it might be one of the most important (for its size) organs in your body. 

Your thyroid gland produces two very important hormones known as T4 and T3 (Thyroxine and Triiodothyronine). 

These hormones are released when triggered by precursor hormones from the brain (known as TSH). 

These hormones then circulate around your entire body to just about every cell and trigger changes at the cellular level. 

These changes result in the production of enzymes and other cellular triggers which help to increase your energy, control your weight, and many other important functions (more on that below). 

What you may not realize is that your body is constantly monitoring changes in your stress level, food intake, and so on and each of these may change how much thyroid your body produces. 

When your body gets the message that you are not consuming enough calories, for instance, it may make changes to how much thyroid hormone it wants your body to produce. 

These small changes may result in big symptoms which may lead you to blog posts like this. 

It can sometimes be difficult to diagnose thyroid problems because the symptoms can be all over the place. 

Do you have dry skin? That could be a thyroid problem. 

Do you have trouble losing weight? That could be a thyroid problem. 

Are you losing your hair? That could be a thyroid problem. 

Are you having trouble getting pregnant? That could be a thyroid problem.

You get the idea. 

So what are you supposed to do?

One of the best things that you can do is take some time to learn the basics of your thyroid gland and how it works/functions. 

10 Important Functions Your Thyroid Is Responsible For

With these basics under your belt let’s talk about the top #10 most important functions that your thyroid is responsible for. 

Just realize as you read through this that these are NOT the only functions that your thyroid gland controls. 

Each person, if they have thyroid problems, may present with slightly different symptoms. 

But these 10 functions are most commonly affected by even small thyroid changes. 

#1. Regulates Your Metabolism & Weight

The first, and perhaps most important, function of your thyroid gland has to do with your metabolism and your weight. 

Your thyroid gland is estimated to be responsible for up to 60% of your metabolism or your basal metabolic rate (1).

Your basal metabolic rate is a rough measurement of how many calories you burn at baseline just doing things that you need to do to survive (2).

Things like breathing, sleeping, thinking, and so on. 

You may not realize that your metabolism (your basal metabolic rate) is one of the most important aspects to measure when you are trying to lose weight. 

Why?

Because your metabolism is responsible for burning thousands of calories (up to 80% of your total daily calories) each and every day. 

If you have too little thyroid hormone in your body then your metabolism will drop. 

If you drop your metabolism by even 20% of normal that may count for up to 400 calories that you aren’t burning each and every day. 

It’s easy to see how this can add up and lead to problems such as weight gain or difficulties with weight loss. 

On the flip side, if you have an overactive thyroid (too much thyroid hormone) then your metabolism may actually increase!

A higher than normal metabolism often leads to weight loss (3) (a good thing for those who are overweight but a bad thing if you are a normal weight). 

Some people believe (wrongly) that they can increase their thyroid dose to help with weight loss. 

This dangerous type of therapy does not work well and generally does not help with weight loss. 

If you are having issues with your weight or you feel that your metabolism isn’t quite what it used to be, then checking your thyroid function is a good next step. 

#2. Controls Hair Growth

It surprises me to know that most patients are often more concerned about the quality and texture of their hair when compared to things like their energy or their weight. 

And your thyroid gland is one of many hormones and nutrients responsible for managing the quality and texture of your hair (4).

Low amounts of thyroid hormone can lead to changes such as rapid hair loss, hair breakage and even thinning of the hair. 

These changes are not taken well by patients and this will often lead people into my office. 

Even high amounts of thyroid hormone (such as seen in hyperthyroidism) can lead to dry, brittle hair and hair loss as well. 

Just remember:

Your thyroid is one of many hormones responsible for hair growth so don’t jump to a thyroid problem if you have hair loss straight away. 

One of the most common causes of hair loss is simply low iron or iron deficiency (5).

Another common cause of hair loss is related to estrogen deficiency in menopause. 

If you are struggling with hair loss or dry, brittle hair then it may be a good idea to check your thyroid but just realize that hair loss can be related to more than just your thyroid. 

#3. Controls Cellular Energy Production

T3 Thyroid hormone, predominately, plays an important role in regulating your subjective sense of energy. 

And by energy, I mean how you are feeling when you wake up in the morning. 

Do you have enough energy to wake up and get started with your day?

Are you able to get going without a cup of coffee?

Do you feel like you crash at midday?

Do you feel like it’s a struggle to focus on your work?

If you have issues with any of these then you may have an energy problem. 

Thyroid hormones may help to regulate your energy by increasing certain enzymes in your mitochondria (6).

Your mitochondria are often referred to as the “powerhouse” of the cell and they produce the energy currency known as ATP. 

Low levels of ATP may be one of the causes of this subjective feeling of low energy that many people suffer from. 

In addition, it has been shown that certain genetic changes predispose patients to persistent fatigue even while taking thyroid medication. 

Patients with the TSHR-Asp727Glu polymorphism (7) (found in around 7% of the population) have more profound fatigue when compared to those without it. 

If you have this genetic defect you may need higher doses of thyroid medication to break through the resistance. 

#4. Controlls Other Hormones

Your thyroid gland may be the “master hormone” in the sense that it controls many other hormones in your body. 

Changes to your thyroid gland may cause a cascade of symptoms from other hormone imbalances. 

We know, for instance, that your thyroid gland helps to regulate the following hormones: testosterone, estrogen, progesterone (8), and even cortisol (9).

What that means for you is that any change to circulating thyroid hormones may lead to changes in these other hormones. 

Do you have low testosterone? Well, that may be the cause of low thyroid hormone (10).

Are you struggling with menstrual irregularities? That may be caused by low thyroid hormone (11).

The list goes on and on. 

Because of these important interactions, it’s important to always look for the “root cause” and treat that if possible. 

If you suffer from low testosterone related to low thyroid hormone then the answer is to fix the thyroid gland which will then fix the testosterone. 

#5. Regulates Fertility

Through its impact on progesterone and estrogen, your thyroid helps to ensure that you can not only get pregnant but maintain pregnancy (12).

Would it surprise you to know that thyroid disease is among the top #3-#5 most common causes of infertility (13)?

It’s right up there with obesity and diabetes and second to menstrual disorders (such as endometriosis). 

This makes thyroid disease a serious, and often underappreciated, cause of infertility among women. 

Many reproductive endocrinologist offices know this and will often give women who come in with fertility issues thyroid hormone medication. 

In my experience, this tends to be true as well. I have found that many women become pregnant after optimizing their thyroid medication. 

If you struggle with infertility don’t forget to evaluate your thyroid function or go to someone who can help adequately assess it. 

#6. Regulates Mood

It isn’t well known how thyroid hormone regulates your mood but it is well established that it does. 

Depression (and even anxiety) tend to be among the most common symptoms of thyroid disorders (14).

Depression tends to be seen in patients who have an underactive thyroid while anxiety tends to be more prevalent in patients who have an overactive thyroid. 

But that pattern isn’t always set in stone. 

I have definitely seen patients with low thyroid present with anxiety and depression or some mix of the two. 

Generally, when you have depression/anxiety from your thyroid you also tend to have other symptoms as well (such as weight gain or fatigue) so don’t assume that all depression is thyroid-related. 

But, if you’ve been treated with multiple anti-depressants in the past and nothing seems to be working then looking at your thyroid would be a wise next step (15).

#7. Manages Your Ability to Concentrate and Remain Focused

Beyond mood, your thyroid also helps to promote normal cognition or brain function. 

Problems with your thyroid can often present with symptoms such as “brain fog” or the inability to think clearly or articulate your words (16).

People with this condition also say they have issues remaining focused, problems concentrating at work, and find themselves forgetting simple things. 

This can be a big problem, especially for your career or work life. 

The inability to remember important dates, especially in careers such as law, medicine, etc. can become a big problem. 

I’ve had more than a few patients come to me with brain fog as their number #1 complaint only to find that it is related to their thyroid. 

#8. Regulates Body Temperature

Your body temperature, also known as basal body temperature, is regulated by your thyroid gland. 

Remember:

Thyroid hormone helps to increase ENERGY production. 

When energy is consumed heat is released. 

As heat is released your body temperature will increase (or stay at a normal level). 

Problems with your thyroid may result in a lower-than-normal body temperature which is often accompanied by fatigue and weight gain due to poor metabolism (17).

This is often an advanced feature that is only seen when patients are severely hypothyroid, but it’s often a good tool to test for because you can do it at home. 

Purchasing a thermometer and checking your temperature first thing in the morning can be a useful proxy for thyroid function. 

It’s obviously not as accurate as checking your thyroid lab tests but it’s a cheap and easy trick that you can take advantage of right away. 

#9. Controls Heart Rate

Thyroid hormone also helps to regulate your heart rate through its influence on calcium channel pumps in your heart. 

T3, especially, is quite powerful at increasing both blood pressure and heart rate when taken as a medication (18).

Your heart rate, like your body temperature, is another tool that you can easily check at home with simple tests such as a blood pressure monitor. 

These monitors will often check both your blood pressure and your resting pulse. 

Your pulse should be somewhere between 70-80 in the rested state. 

If you have a heart rate that is in the 50s that may be a sign of a thyroid problem. 

Much like testing your body temperature, this isn’t as accurate as testing for your blood levels, but it’s an easy tool and a relatively cheap test. 

High levels of thyroid hormone (such as seen in hyperthyroidism or in excessive thyroid medication dosing) can cause the opposite effect and lead to an increased heart rate. 

If you are taking thyroid medication and you find that your resting heart rate is in the 100s or 110s then that may be a sign you are taking too much thyroid hormone. 

#10. Regulates The Menstrual Cycle

Lastly, your thyroid also helps to regulate the menstrual cycle in women. 

The menstrual cycle is something that is highly regulated by many hormones including: FSH, LH, estradiol, and progesterone. 

Thyroid hormone, as you already know, can influence both progesterone and estradiol which may alter the frequency and quality of your menstrual cycle. 

Women with low thyroid function may present with anovulatory cycles (leading to infertility), delayed or prolonged menstrual cycles, or changes to their flow. 

An increase in thyroid hormone often leads to rapid but very short menstrual cycles usually less than 20 days apart. 

If you are suffering from menstrual issues or infertility then assessing your thyroid should be a top priority. 

Types of Thyroid Problems

Hopefully, you’re beginning to get the idea that there are MANY things that can go wrong with your thyroid gland. 

The good news is that some of the problems associated with your thyroid have no effect on thyroid hormone production. 

What does that mean?

It means that even if you have a condition such as thyroid cancer or a thyroid nodule, there’s a low chance that it will interfere with thyroid function in your body. 

That means you probably won’t have the symptoms we discussed above. 

But, on the other hand, there are some conditions that primarily do alter your ability to produce thyroid hormone. 

These conditions, such as Hashimoto’s thyroiditis, WILL cause symptoms. 

To give you a better idea of what can go wrong with your thyroid I’ve included some of the most common problems below: 

• Low thyroid production (known as hypothyroidism) – Very common with up to 10% of patients suffering from this condition
• High thyroid production (known as hyperthyroidism) – Not as common as hypothyroidism with an incidence of up to 1-2% of the population suffering from this disease (19)
• Thyroid nodules (usually these do not interfere with thyroid hormone production at all) – VERY common with up to 20% of the population having a thyroid nodule (20)
• Autoimmune disease where your own body attacks your thyroid gland (known as Hashimoto’s thyroiditis) – Somewhat common with up to 5% of patients suffering from this condition (21)
• Inflammation of the thyroid gland from infection, trauma or immune attack (known as Thyroiditis) 
• Cancer of the thyroid gland (this type of issue usually does not interfere with thyroid hormone production) – Thyroid cancer is the most common cancer of the endocrine system but has a 5-year survival rate of around 97%

Figuring out what is wrong with your thyroid (if anything) is of utmost priority. 

When you go to your Doctors office make sure you walk out with a diagnosis or at least an idea as to what is going on. 

If you don’t then you may end up frustrated without any real clear idea of how to treat your issue. 

Your Next Steps

So what should you do next after reading this article, especially if you suspect you have some sort of thyroid problem?

Your best bet is to follow the 6 steps listed below: 

• #1. Go visit your doctor (try to find a doctor who specializes in thyroid disorders)
• #2. Get a complete thyroid lab panel (TSH, free T3, free T4, reverse T3, thyroid antibodies)
• #3. Determine what is wrong with your thyroid (do you have a sluggish thyroid or an overactive thyroid?)
• #4. Eat healthy, exercise, and reduce your stress
• #5. Consider using high-quality supplements to support thyroid function
• #6. Take thyroid medication (if necessary)
• #7. Get re-tested and monitor your symptoms to ensure that you are on the right track

These steps are designed to help get you started on the right track so you can get back to feeling healthy and back to normal. 

Always remember that each person is unique and may present slightly differently so it’s difficult to fit everyone into a simple “treatment box” but using this approach should help. 

Now I want to hear from you:

Do you suspect you have issues with your thyroid?

Are you experiencing symptoms associated with any of the 10 functions we discussed above?

Have you been tested for thyroid problems?

What, if anything, did your lab tests show?

Leave your comments below!