Did you know that around 20 million people in the U.S. are living with some form of thyroid disease? It’s more common than most people realize and often misunderstood. Whether you’ve been diagnosed, are noticing symptoms, or just want to stay informed, getting a handle on thyroid basics is a smart move for your overall health.

In this post, we’ll break down what the thyroid does, why it matters, and how things can go off track. You’ll learn about the two most common conditions—hyperthyroidism and hypothyroidism. Plus, we’ll explore how autoimmune issues can affect your thyroid, what symptoms to keep an eye on, and which blood tests give you the full picture (hint: it’s not just TSH).

Understanding How Your Thyroid Works

Your thyroid is a small, butterfly-shaped gland at the base of your neck—about the size of a walnut. As part of your endocrine system, it produces hormones that help regulate everything from your metabolism to your mood.

Here are the key hormones it produces:

· Thyroxine (T4) and Triiodothyronine (T3) — These are your metabolic powerhouses. They influence energy levels, digestion, hormone balance, mood, and more.

· Calcitonin — This hormone helps manage calcium levels in your blood, supporting bone health and nerve function.

Think of your thyroid as your body’s internal thermostat. It helps control how fast or slow things run—like your heart rate, body temperature, and even how clearly you think. When it’s working well, you probably don’t notice it. But when it’s off, the ripple effects can be hard to ignore.

So, what happens when the thyroid speeds up or slows down? Let’s take a closer look at the signs and symptoms of thyroid dysfunction.

Hyperthyroidism: Signs and Symptoms

Hyperthyroidism occurs when the thyroid gland produces excessive amounts of thyroid hormones, leading to an overactive metabolism. One of the most common concerns related to hyperthyroidism is difficulty maintaining a healthy weight. When the thyroid is overactive, the body's metabolic processes speed up, making it challenging to manage weight effectively. Hyperthyroidism can also lead to a variety of other symptoms, including:

Irregular Heartbeat: Palpitations or an irregular heartbeat can occur due to excess thyroid hormone and its impact on the cardiovascular symptom.
Anxiety and Tremors: Elevated thyroid hormone levels can affect the nervous system, leading to heightened anxiety, irritability, and even tremors, particularly in the hands.
Increased Sweating or Heat Intolerance: The body's elevated metabolic rate can cause excessive sweating and an intolerance to heat.
Fatigue: A common symptom due to the body's heightened state of activity.
Frequent Bowel Movements or Diarrhea: The digestive system can be significantly affected, leading to more frequent bowel movements or diarrhea.
Irregular Menstrual Cycles: Women with hyperthyroidism may experience irregular or lighter menstrual periods.
Insomnia or Trouble Sleeping: The overactive thyroid can disrupt sleep patterns, making it difficult to fall or stay asleep.
Thinning or Brittle Hair: Hair may become thinner or more brittle.
Restlessness: A general sense of restlessness or inability to relax is common among those with hyperthyroidism.

Hyperthyroidism impacts about 1.3% of the U.S. population. It also accounts for a minority of thyroid disease—with about 20-22% of those who suffer from thyroid disorder having hyperthyroidism.

Hypothyroidism: Signs and Symptoms

Hypothyroidism, on the other hand, occurs when the thyroid gland does not produce enough thyroid hormones, leading to a sluggish metabolism. This condition is often linked to weight gain or difficulty losing weight. The reduced production of thyroid hormone can manifest in various ways, including:

Low Energy or Fatigue: A persistent feeling of tiredness or low energy is one of the most common symptoms of hypothyroidism.
Feeling Cold: Many individuals with hypothyroidism feel unusually cold, especially in the extremities like the hands and feet.
Constipation: It can affect digestion, leading to constipation.
Dry Skin and Hair Thinning or Brittleness: Skin may become dry, and hair may fall out or become thin or brittle.
Puffy Face and Swelling: Some people experience facial puffiness and swelling in the hands, feet, or legs.
Dry Skin or Eczema: Dry skin or eczema, particularly during the winter months, can be indicative of hypothyroidism.
Depression or Anxiety: Mood changes, including depression or anxiety, are common due to the hormonal imbalances.
Brain Fog and Forgetfulness: Cognitive functions can be affected, leading to brain fog and forgetfulness.
Joint Aches, Pains, or Weakness: Musculoskeletal issues, such as joint aches, pains, or weakness frequently occur.
Irregular or Heavy Menstrual Cycles: Women with hypothyroidism may experience irregular or heavier menstrual periods.
Fertility Issues or Infertility: Hypothyroidism can impact fertility and may lead to difficulties conceiving.
Low Libido: A decreased sex drive is another common symptom.
Brittle Nails: Nails may become brittle and prone to breaking.
Thinning of the Outer Third of the Eyebrows: Some individuals notice thinning of the outer third of their eyebrows.

Hypothyroidism impacts about 4.6% of the U.S. population, with most being mild or subclinical cases. It also accounts for most of the thyroid disease—with about 78-80% of those who suffer from thyroid disorder having hypothyroidism.

Other Thyroid Disorders to Watch

While hyperthyroidism and hypothyroidism are the most commonly discussed thyroid conditions, the thyroid gland can be affected by a range of other disorders. These may not always present with dramatic symptoms, but they’re worth knowing about—especially if you’re monitoring your thyroid health or navigating a diagnosis.

· Goiter — A visible or palpable enlargement of the thyroid gland, often linked to iodine deficiency or another underlying thyroid dysfunction.

· Thyroid Nodules — Small lumps or growths within the thyroid. Most are benign, but some may require imaging or biopsy to rule out malignancy.

· Thyroiditis — Inflammation of the thyroid, which may be caused by autoimmune conditions, infections, or postpartum changes. Symptoms can vary and may resolve over time.

· Thyroid Cancer — Although rare, thyroid cancer is typically treatable, especially when detected early. Regular screening and prompt evaluation of suspicious nodules are key.

Autoimmune Thyroid Diseases: Graves’ and Hashimoto's

There is also an autoimmune component of thyroid disease. In fact, the most frequent issues involving thyroid are autoimmune. When the thyroid is overactive and accompanied by an autoimmune component, the condition is known as Graves' disease. Conversely, when the thyroid is underactive and autoimmune-related, it's called Hashimoto's thyroiditis.

The statistics below illustrate how thyroid disorders are often accompanied by autoimmune disease.

· Approximately 60-80% of hyperthyroidism cases are due to Graves' disease.

· About 90% of hypothyroidism cases stem from Hashimoto's thyroiditis.

In my clinical experience spanning over a decade, I've observed that many patients are underdiagnosed and, consequently, undertreated for the autoimmune component of these conditions. This is often due to standard testing protocols that may not be comprehensive enough. But we'll explore this further in a later section.

Understanding Autoimmune Disease

Since thyroid disorders are often accompanied by autoimmune disease, let’s spend some time understanding what that means.

Autoimmune diseases are prevalent in the United States, affecting roughly 17-27 million Americans. Graves' and Hashimoto's are among the most common. Autoimmune conditions occur when the body's immune system mistakenly attacks healthy tissues. In the case of thyroid disease, this means the immune system targets the thyroid gland.

Several factors can contribute to autoimmune thyroid conditions, including:

Infections (viruses, bacteria, parasites, fungus).
Environmental toxins (chemicals, mold, pesticides, herbicides).
Acute or chronic stress.
Gut health imbalances (dysbiosis).
Nutrient deficiencies (B vitamins, vitamin D, magnesium, selenium, minerals).
Blood sugar imbalance.
Adrenal fatigue/HPA axis dysregulation.

Unfortunately, many autoimmune thyroid conditions go undiagnosed or are treated with medications that only address symptoms rather than the root cause. For example, patients with hypothyroidism or Hashimoto's may be prescribed levothyroxine or desiccated thyroid medication, while those with Graves' may receive methimazole to suppress thyroid activity. While these treatments can certainly be helpful, they do not address the underlying autoimmune component. This is where functional medicine sets itself apart by identifying and addressing the root cause. Before we can address the root cause, though, we need to identify it. That comes through testing.

Thyroid Testing: Standard vs. Functional Medicine Approaches

Let's compare the standard American model of thyroid testing with the functional medicine approach.

Standard American Model:

Typically tests: TSH and T4

Functional Medicine Model:

Usually tests: TSH, T4, T3, free T4, free T3, TPO/TSI antibodies, and reverse T3 (rT3)

The difference is significant. The standard model often misses key markers, leading to decades of undiagnosed thyroid disease for many patients. Let's break down these markers:

TSH (Thyroid Stimulating Hormone): Produced by the pituitary gland, TSH stimulates the thyroid to produce more hormone. In Graves' disease, TSH levels are typically low due to an overabundance of thyroid hormones. In Hashimoto's, TSH levels are often high as the hormone struggles to stimulate a non-responsive thyroid.
T4 (Thyroxine): Contains four iodine atoms and makes up about 99% of thyroid hormone.
T3 (Triiodothyronine): Contains three iodine atoms and accounts for about 1% of thyroid hormone production.
Free T4 and Free T3: These are the unbound forms of T4 and T3, readily available for the body to use. Both are important to check.
Reverse T3 (rT3): Indicates how much of the T3 hormone is stored versus used. Higher levels suggest that less T3 is bioavailable for daily tasks.
TPO/TSI Antibodies: TPO (Thyroid Peroxidase) antibodies indicate the presence of Hashimoto's or an underactive autoimmune condition. TSI (Thyroid Stimulating Immunoglobulins) antibodies, when elevated, strongly suggest Graves' disease or an overactive autoimmune thyroid condition.

Comprehensive thyroid testing is essential for accurate diagnosis and effective treatment. Without it, millions of people may remain undiagnosed and continue to feel unwell.

How Functional Medicine Supports Thyroid Health

Functional medicine takes a holistic approach to thyroid care. Instead of focusing solely on symptoms or relying on one-size-fits-all treatments, it aims to uncover and address the root causes of dysfunction, which leads to more accurate diagnoses and longer-lasting results.

Obviously, that starts with the comprehensive testing process we outlined above. It also extends to treatment by recognizing that thyroid health is deeply interconnected with other systems in the body. Consequently, treatment plans are holistic in nature and personalized to each patient. For example, though, a functional medicine thyroid treatment plan may include elements such as:

· Balancing the nervous system to reduce overstimulation and support emotional resilience.

· Restoring gut health by addressing dysbiosis, leaky gut, and nutrient absorption.

· Identifying and removing toxins, infections, and heavy metals that may be triggering immune dysfunction.

· Supporting the stress response and HPA axis by regulating adrenal function and cortisol levels.

· Stabilizing blood sugar to reduce metabolic stress on the thyroid.

· Correcting nutritional deficiencies such as vitamin D, selenium, iodine, B vitamins, and magnesium.

· Using adaptogens and lifestyle strategies to help the body manage daily stress more effectively.

Rather than treating the thyroid as an isolated problem, functional medicine views it as part of a larger system that needs to be nourished and rebalanced. Every treatment plan is customized—there’s no standard protocol—because every person’s biology, history, and lifestyle are unique.

By focusing on restoration rather than symptom suppression, functional medicine often leads to powerful, lasting improvements in energy, mood, metabolism, and overall vitality.

Next Steps

If you’ve been struggling with any of the symptoms above, or don’t feel like your doctor has taken you seriously, let’s get you some help! I aim to always get to the root cause of health issues by first starting with comprehensive evaluation of any health issue. Reach out to Dr. Veronika Vlasov, a Functional Medicine Doctor out of Elmhurst IL.