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Overactive Thyroid vs. Underactive Thyroid: What it Means

The thyroid is a small gland in your neck that controls your metabolism and influences how you think and feel. It does this by producing the hormones thyroxine (T4) and triiodothyronine (T3), which tell your body’s cells how much energy to use to function optimally.

Your thyroid is an amazing gland that has an enormous impact on your overall health, but some thyroids can be overactive or underactive. Here’s how to tell if yours is working too hard or too little.

If something feels off in your body, start with watching our free thyroid webinar.

Overactive Thyroid vs. Underactive Thyroid

Thyroid disorders are common, and the two most common – hypothyroidism and hyperthyroidism – have important differences in their symptoms and causes.  The major difference between hypothyroidism and hyperthyroidism is the amount of hormones being produced.

For hyperthyroidism, it’s easy to remember that ‘hyper’ means too much. Hence, the thyroid is over-producing hormones and considered overactive. On the other hand, hypothyroidism is when your thyroid is not producing enough hormones, so it is considered underactive. Despite their differences, both conditions affect how you feel and can be quite debilitating if left untreated. Let’s dive deeper into each of the thyroid conditions.


Patients with overactive thyroids may experience a wide range of symptoms. Keep in mind, however, that the symptoms of hyperthyroidism can mimic many other conditions, making it difficult to diagnose. So, it’s important you get to the bottom of the symptoms you’re experiencing.

Symptoms of an Overactive Thyroid

If you have hyperthyroidism, you might experience any of the following symptoms:

  • Unintentional weight loss, even without dietary changes
  • Rapid heartbeat
  • Irregular heartbeat or heart palpitations
  • Increased appetite
  • Mood changes, including nervousness, anxiety, and irritability
  • Tremors in your hands and fingers
  • Excessive sweating
  • Changes in your menstrual cycle
  • New or worsened heat intolerance
  • More frequent bowel movements
  • An enlarged thyroid gland, also known as goiter
  • Fatigue
  • Weak muscles
  • Difficulty sleeping
  • Thinner skin that is more susceptible to cuts and bruises
  • Fine hair that breaks easily

Causes of Hyperthyroidism

The most common cause of hyperthyroidism is an autoimmune disorder called Graves’ disease. With Graves’ disease, your body releases antibodies that make your thyroid gland produce too much T4.

Additionally, if you develop inflammation or goiter in your thyroid gland, your thyroid could become overactive and trigger hyperthyroidism.

When to See a Functional Medicine Doctor

Unexplained weight loss, heart palpitations, hand tremors, or excessive sweating are all causes of concern. Since many of these signs could be associated with other conditions, it’s usually best to see a functional medicine doctor to determine the root cause of your symptoms, whether or not you are suffering from hyperthyroidism, and discover how to restore your health.  


When your thyroid is underactive, things in your body can start to slow down. However, with hypothyroidism, you may have few or no symptoms, or you may mistake symptoms for the expected effects of aging.

Symptoms of an Underactive Thyroid

Hypothyroidism tends to develop slowly. At first, you might not even notice the symptoms as unusual. But as your metabolism continues to slow, you may develop more obvious problems, such as:

  • Unintentional weight gain, even without dietary changes
  • Fatigue
  • Chronic hoarseness
  • Dry skin
  • Constipation
  • Puffy face
  • Joint pain
  • Muscle aches or weakness
  • New or worsened cold intolerance
  • Thinning hair or hair loss
  • Heavy or irregular menstrual cycles
  • Infertility
  • Goiter

Causes of Hypothyroidism

People usually develop hypothyroidism later in life, which is why symptoms are often thought to be an early part of aging. The most common cause of hypothyroidism is an autoimmune disease known as Hashimoto’s, a condition that causes your body’s immune system to produce antibodies that attack your thyroid gland.

Additionally, pregnancy, certain medications, and a diet low in iodine can trigger an underactive thyroid.

When to See a Functional Medicine Doctor

If you have any of the hypothyroidism symptoms listed above, you may want to see your functional medicine doctor to get to the root of what’s causing your symptoms. Again, since some of the signs can easily be mistaken for aging or stress, it’s better to rule out hypothyroidism as the cause than to leave it untreated.

Want to know more about the difference between hypothyroidism and hyperthyroidism? Check out our free webinar.

Can You Have Both an Overactive Thyroid and an Underactive Thyroid?

You may be wondering: can you have both an overactive and underactive thyroid at the same time?

Fortunately, the short answer to this question is “no.” But while you can’t simultaneously experience hypothyroidism and hyperthyroidism, it is possible to transition from one condition to the other, meaning you could experience both an overactive and underactive thyroid in your lifetime. The transition from one thyroid disorder to another is rare, but it can happen either as a result of improper treatment or a spontaneous shift in your body.

Regardless of whether it’s an underactive or overactive thyroid, the irregular production of the thyroid hormones is at the root. Ignoring thyroid disorders can lead to more serious health issues, so if you’ve been diagnosed with hyperthyroidism or hypothyroidism, it is crucial that you work with a functional medicine doctor to restore balance and get your body operating correctly.

How Are Thyroid Disorders Diagnosed?

Thyroid disorders can be very complex. A functional medicine doctor will work with you to gather your detailed medical history, perform a physical exam, and run appropriate testing.

When it comes to lab testing, conventional testing for thyroid conditions is often inadequate, as most physicians test only for thyroid stimulating hormone (TSH) levels. Testing for just TSH is problematic because it does not reveal how much active thyroid hormone you have, nor does it indicate whether you may have autoimmune disease contributing to your thyroid issues.

At Tri-Cities Functional Medicine, we assess thyroid function with comprehensive thyroid lab testing to measure your hormone levels. We also run tests to look for antibodies that attack the thyroid gland.

Treating Thyroid Disorders with Functional Medicine

As you can see, the symptoms and causes for hyperthyroidism and hypothyroidism are polar opposites – unexplained weight loss vs. weight gain, heat intolerance vs. cold intolerance, increased bowel movements vs. constipation. However, since the thyroid regulates your metabolism, both conditions can affect your overall health. And while there is no known cure for either condition, a functional approach can help you balance your overall hormones and restore thyroid function to normal.

The functional medicine approach to thyroid disorders seeks to address the underlying causes rather than suppress symptoms. While conventional treatment methods that use medications aim to manage thyroid disorders, there are other options that address the root cause of your discomfort and help you achieve full-body wellness.

Once your doctor has run labs and confirmed that you have a thyroid condition, they will begin to look for underlying factors. These factors could include gut imbalances, gluten sensitivity, chronic infections, exposure to environmental toxins, nutrient imbalances, and more.

To address these root causes, a functional medicine doctor will build a treatment plan that includes diet and lifestyle changes, smart supplementation, stress reduction, and medications if necessary.

You don’t have to suffer through conventional treatments for thyroid disorders, which involve taking medication at increasingly higher doses, causing unpleasant side effects. Tri-Cities Functional Medicine offers holistic solutions to thyroid disorders that support full healing and help you thrive again.

If you exhibit symptoms of thyroid disorder, take the first step:

  1. Watch a free webinar to learn about our approach to the health concerns you are facing.
  2. Schedule a Free Discovery Call to  discuss your health concerns and goals to see if our practice is a good fit for you.
  3. After your discovery call – if we are a good fit, you’ll schedule a consultation with our doctor to dive deeper and formulate an individualized treatment plan for you.

Tri-Cities Functional Medicine is located in Johnson City, Tennessee, and serves patients throughout Tennessee and into Virginia, North Carolina, West Virginia and Kentucky. These areas include but are not limited to: Washington County, TN, Sullivan County, TN, Carter County, TN, Greene County, TN, Knox County, TN, Bristol, TN, Holston Valley, TN, Tri-Cities, TN, Walnut Hill, TN, Elizabethton, TN, Greeneville, TN, Morristown, TN, Blountville, TN, Bluff City, TN, Kingsport, TN, Jonesborough, TN, Colonial Heights, TN, Limestone, TN, Knoxville, TN, Bristol, VA, Abingdon, VA, Grundy, VA, Asheville, NC, Boone, NC.