9 Most Commonly Ordered Functional Medicine Thyroid Labs

According to the American Thyroid Association, over 20 million Americans live with thyroid disease, yet up to 60% are unaware of their condition: this means that comprehensive thyroid testing has never been more essential. These undetected imbalances can rob a person of her or his quality of life, affecting everything from energy levels to mood, fertility, and overall health. 

Identifying thyroid imbalances is key, and functional medicine provides a more thorough approach to testing than standard methods.

This article is a comprehensive guide to the nine most commonly ordered thyroid labs in functional medicine. We will explore the physiology behind each test, explain why each is essential for assessing thyroid health, and highlight the importance of comprehensive testing for accurate diagnosis and effective treatment.

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What is Functional Medicine?

Functional medicine is a holistic approach to healthcare that focuses on identifying and addressing the root causes of health issues, not just treating symptoms. It emphasizes personalized care, considering an individual’s genetics, environment, and lifestyle. 

Comprehensive lab testing is a cornerstone of functional medicine because it allows practitioners to understand the root cause of a person’s condition.

Why General Thyroid Testing May Miss Critical Information

Conventional thyroid testing typically involves only two tests:‍

Thyroid-Stimulating Hormone (TSH)

TSH is typically the initial test run to assess thyroid function; if excessively high or low, a free or total T4 may then be run. However, many functional medicine providers feel that the upper limit of TSH misses many individuals with symptomatic thyroid dysfunction, especially when run as a single biomarker.  

The thyroid hormone T4 (Thyroxine)

While these tests are useful, they may fail to detect subtle imbalances or underlying issues. Many individuals with normal TSH and Free T4 levels still experience symptoms of thyroid dysfunction, which comprehensive testing can uncover.

Missed Diagnoses

Standard tests often miss autoimmune thyroid disease or issues with converting T4 to T3. Comprehensive testing can catch these imbalances.

Conditions like Hashimoto’s thyroiditis or Graves’ disease require antibody testing, which standard panels do not include.

Poor conversion of T4 to T3 is important to catch in people who have persistent hypothyroid symptoms despite having “normal” labs. 

Symptoms of Thyroid Dysfunction

Recognizing thyroid symptoms is the first step in seeking timely treatment. Symptoms can vary and affect different body systems:

Hypothyroid Symptoms (Underactive Thyroid)

• Fatigue

• Weight gain

• Cold intolerance

• Dry skin

• Hair loss

• Constipation

• Depression or low mood

• Slow heart rate (bradycardia)

• Muscle weakness or cramps

• Memory problems or difficulty concentrating ("brain fog")

• Puffy face

• Hoarseness

• Irregular or heavy menstrual periods

• High cholesterol levels

• Joint pain or stiffness

Hyperthyroid Symptoms (Overactive Thyroid)

• Weight loss

• Heat intolerance

• Rapid or irregular heartbeat (tachycardia) and/or heart palpitations

• Nervousness or anxiety

• Tremors (shaking hands)

• Increased sweating

• Fatigue or muscle weakness

• Difficulty sleeping (insomnia)

• Frequent bowel movements or diarrhea

• Irritability or mood swings

• Bulging eyes (in Graves' disease)

• Thinning skin

• Fine, brittle hair

• Irregular or light menstrual periods

• Increased appetite

The Importance of Recognizing Thyroid Symptoms

Our culture has normalized unwellness, but that doesn’t mean that living with symptoms of thyroid dysfunction is normal.

Early detection and treatment can significantly improve quality of life and prevent some long-term complications, which we’ll explore below. 

Consequences of Thyroid Dysfunction

Living with thyroid dysfunction can put people at risk for long-term health conditions.

For example, chronic complications of hypothyroidism can include:

• High cholesterol

• Heart problems: congestive heart failure, risk of arrhythmia

• Electrolyte imbalance, especially low sodium

• Memory loss and brain fog 

• Carpal tunnel syndrome

• Sleep apnea

• Infertility

Chronic complications of hyperthyroidism can include: 

• Cardiovascular events, including atrial fibrillation and stroke

• Osteoporosis

• Infertility

• Thyroid Storm: this is a life-threatening complication of untreated hyperthyroidism, characterized by severe tachycardia, hyperthermia, and multi-organ dysfunction, with a high mortality rate, especially in older individuals.

Benefits of Functional Medicine Testing for Thyroid Health

Functional medicine integrates multiple lab tests to form a complete picture of thyroid health. This approach considers individual differences in hormone levels and metabolism, offering a more nuanced understanding compared to standard testing.

For example, unlike standard testing, functional medicine may assess Reverse T3 and Thyroid Antibodies to uncover hidden imbalances and autoimmune factors keeping your thyroid gland from functioning optimally.

The 9 Most Commonly Ordered Thyroid Functional Medicine Labs

Below are the 9 most commonly ordered thyroid labs in Functional Medicine:

1. Thyroid-Stimulating Hormone (TSH)

Physiology

Thyroid-Stimulating Hormone (TSH), a hormone from your anterior pituitary gland, directs thyroid hormone production (T4 and T3) by signaling the thyroid gland to maintain metabolic balance. The less thyroid hormone the thyroid gland releases, the more TSH is released. 

Significance in Thyroid Assessment

TSH is a foundational indicator of thyroid function. 

However, TSH interpretation has its challenges because, while the current reference range is generally set between 0.4-5.49 mIU/L, research shows that an increased incidence of disease occurs in patients trending toward the high end (towards hypothyroidism) and the low end (towards hyperthyroidism) of the TSH reference range.

TSH should be interpreted within the context of an individual’s medical history and current symptoms, as well as using other biomarkers for a comprehensive clinical picture.

Practical Tips

• Timing: TSH levels are best measured in the morning when hormone levels are most stable.

• Consistency: having the test done at the same time each day can improve reliability, as hormone levels can fluctuate throughout the day.

2. & 3. Free and Total T4 (Thyroxine)

Physiology

T4, or thyroxine, is the primary hormone produced by the thyroid gland. T4 is considered a prohormone, meaning that it becomes most active when it is converted to the more active T3 hormone. 

T4 travels in the bloodstream on proteins (bound), until it is released (free) and converted to T3. 

There are two types of T4 measurements:

• Total T4: measures both bound (attached to proteins in the blood) and unbound (free) T4.

• Free T4: measures only the unbound, active T4 that is available for use by the body's tissues.

Significance in Thyroid Assessment

• Total T4: provides a total picture of T4 hormone levels in your blood, including bound and free forms. This reveals a complete picture of the thyroid gland’s production of T4.

• Free T4: this test helps doctors understand how much T4 is available to be converted to T3 and support your body’s metabolic processes. Alterations in the ratio of total to free T4 may indicate shifts in thyroid hormone production, usage, or in the amount of binding protein available. 

Practical Tips

• Balanced Assessment: evaluating both free and total T4 levels provides a comprehensive understanding of total T4 thyroid hormone availability.

4. & 5. Free and Total T3 (Triiodothyronine)

Physiology

T3, or triiodothyronine, is the more active form of thyroid hormone. A small amount of T3 is made in the thyroid gland, but most comes from the conversion of T4 to T3 in the body’s tissues. 

Similar to T4, there are two measurements:

• Total T3: Includes both bound and unbound T3 in the blood.

• Free T3: Measures only the active, unbound T3 that is available for use by the body.

Significance in Thyroid Assessment

• Metabolic Impact: T3 directly influences your metabolism, energy levels, and overall metabolic rate. Abnormal T3 levels, either too high or too low, can lead to significant health issues.

• Diagnosing Specific Conditions: helps diagnose conditions like hyperthyroidism and T3 toxicosis (excessive T3), which may not be evident through TSH and T4 tests alone.  

• Conversion Efficiency: when tested alongside T4, it evaluates how effectively your body is converting T4 to the active T3 form.

• Binding Issues: high or low free thyroid hormone levels can signal a change in binding protein availability.

Practical Tips

• Therapy Monitoring: essential for patients on T4 therapy (e.g., levothyroxine) to ensure adequate conversion to T3, and for patients on combined T3 and T4 therapy.

• T3-Specific Disorders: important for diagnosing disorders that specifically affect T3 levels, providing a more detailed understanding of thyroid health.

6., 7. & 8.Thyroid Antibodies (TPOAb, TgAb and TSI)

Physiology

• TPOAb (Thyroid Peroxidase Antibodies): these antibodies attack thyroid peroxidase, an enzyme required for thyroid hormone production. High levels indicate an autoimmune response against the thyroid gland.

• TgAb (Thyroglobulin Antibodies): these antibodies target thyroglobulin, a protein involved in thyroid hormone synthesis. Elevated levels also suggest an autoimmune thyroid attack.

• TSI (Thyroid-Stimulating Immunoglobulin): these antibodies mimic the action of TSH, leading to excessive stimulation of the thyroid gland. Elevated TSI levels are primarily associated with Graves' disease, an autoimmune condition causing hyperthyroidism.

Significance in Thyroid Assessment

• Autoimmune Detection: elevated thyroid antibodies are markers of autoimmune thyroid diseases such as Hashimoto’s thyroiditis (leading to hypothyroidism) and Graves’ disease (leading to hyperthyroidism).

• Underlying Causes: discovering these antibodies helps identify the root cause of thyroid dysfunction, allowing for more targeted and effective treatment strategies.

Practical Tips

• Comprehensive Diagnosis: testing for thyroid antibodies is essential for a full thyroid assessment, especially in symptomatic patients and patients with a family history of autoimmune thyroid disease.

• Guiding Treatment: antibody testing helps tailor treatment plans to address the underlying autoimmune response.

9. Reverse T3 (rT3)

Physiology

Reverse T3 (rT3) is an inactive form of thyroid hormone produced when thyroxine (T4) is converted by type 3 deiodinase into an unusable form of T3. 

Unlike the active form, triiodothyronine (T3), rT3 does not have metabolic activity, meaning it does not contribute to the stimulation of metabolism, energy production, or other thyroid-related functions. 

The body produces rT3 as a natural process to regulate thyroid hormone levels, but during times of stress or illness, rT3 levels may increase as a way for the body to reduce energy expenditure and slow metabolism.

Monitoring rT3 levels can provide insight into how the body is managing energy and thyroid function, especially in people with thyroid-related symptoms.

Significance in Thyroid Assessment

• Hormone Conversion Issues: elevated rT3 levels can indicate problems with the conversion of T4 to active T3, which can lead to symptoms of hypothyroidism despite normal TSH and T4 levels.

• Stress Impact: testing reverse T3 helps assess how chronic stress or illness affects thyroid hormone activity, providing insights into chronic conditions and euthyroid sick syndrome.

Practical Tips

• Chronic Stress Management: reverse T3 is useful for identifying patients who may benefit from stress reduction techniques to improve thyroid function.

• Understanding Illness Impact: this test helps in understanding how non-thyroidal illnesses can affect thyroid hormone levels and overall health.

Uncovering Thyroid Imbalance: Next Steps

If you are concerned about your thyroid health and looking for answers, it’s important to work with a medical professional who can help you navigate the process of understanding your lab results and implementing the appropriate therapies to help you recover. 

Consult with a Functional Medicine Healthcare Provider

Professional Guidance: receive expert advice on ordering the appropriate thyroid tests, and their relevance to your symptoms.

Expert Interpretation: benefit from comprehensive analysis of lab results to develop a treatment plan tailored to you.

Take Proactive Steps Towards Optimal Thyroid Health

Your functional medicine provider may or may not recommend thyroid medication. Regardless of whether medication is part of your plan, following essential diet and lifestyle recommendations provides the foundation for long-term thyroid health:

Anti-Inflammatory Diet 

Following a diet rich in whole, unprocessed foods can reduce inflammation that negatively affects thyroid function. Focus on vegetables, fruits, lean proteins, healthy fats (like omega-3s from fish), and avoid inflammatory foods like refined sugar, processed foods, and trans fats.

Adequate Sleep

Prioritizing 7-9 hours of quality sleep supports thyroid hormone production and regulation. Sleep also helps to reduce stress, and stress reduction is important for maintaining balanced thyroid function.

Toxin Avoidance

Minimize exposure to environmental toxins such as pesticides, heavy metals, and endocrine disruptors (like BPA and phthalates), which can interfere with thyroid health. Opt for organic foods and natural cleaning and personal care products when possible.

Stress Reduction

Chronic stress can suppress thyroid function by disrupting the hypothalamic-pituitary-thyroid (HPT) axis. Practices like mindfulness, yoga, deep breathing, and regular physical activity help lower stress levels and support thyroid health.

Balanced Nutrients

Ensure adequate intake of thyroid-supporting nutrients, like iodine (from seaweed or iodized salt), selenium (from Brazil nuts), zinc (from seeds, nuts, and meats), and vitamin D. 

These nutrients are essential for proper thyroid hormone production and function; however, it is important to understand that all supplements should be used under the direction of a licensed healthcare professional. Too much iodine can impair thyroid function. 

Regular Monitoring

Schedule follow-up tests to ensure sustained thyroid health and adjust treatments as needed. You and your healthcare provider will determine the optimal time frame for your long-term thyroid assessment. 

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Key Takeaways

Thyroid disorders are common yet often go undiagnosed, making comprehensive testing essential for accurate diagnosis.

Standard thyroid tests may miss important imbalances: conventional tests, like TSH and T4, may fail to detect subtle thyroid dysfunctions such as autoimmune diseases or hormone conversion issues, highlighting the need for a more in-depth testing approach used in functional medicine.

Functional medicine offers a holistic and personalized approach: by integrating comprehensive thyroid tests, including Reverse T3 and thyroid antibodies, functional medicine practitioners can uncover hidden imbalances, providing a clearer diagnosis and more targeted treatments for optimal thyroid health.