As a naturopathic doctor in clinical practice, it seems all too common that a patient presents with symptoms of thyroid disease but has been told by other doctors their thyroid is "normal" based on a single TSH test. 

Thyroid-stimulating hormone, or TSH, is an important screening and diagnostic tool for thyroid disorders. In conventional medicine, TSH levels falling within a standard reference range are considered normal. However, functional medicine takes a more nuanced approach, emphasizing individualized and optimal ranges and understanding the limitations of TSH alone in diagnosing thyroid dysfunction, especially in its early stages. Recognizing that optimal TSH levels vary based on individual needs, functional medicine provides a holistic approach to thyroid imbalances, promoting a deeper understanding of thyroid health.

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What is the Thyroid, and What is TSH?

The thyroid gland is a butterfly-shaped endocrine in the neck responsible for synthesizing and secreting two thyroid hormones. The thyroid produces approximately 90% inactive thyroid hormone, thyroxine (T4), and 10% active thyroid hormone, triiodothyronine (T3). Once T4 is in circulation, it is converted as needed to T3 or, in some cases, to an alternative inactive thyroid hormone called reverse T3 (rT3). Optimal thyroid function is critical for human health because it acts as the master regulator of metabolism and impacts nearly every aspect of human physiology, including: 

• Energy production
• Body weight
• Heart and respiratory rates
• Digestion
• Nervous system
• Immune system
• Male and female fertility
• Cholesterol levels
• Body temperature
• Muscle strength and mass

What Is TSH?

TSH is a hormone produced by the brain's anterior pituitary gland. It is used as the primary screening marker for thyroid function. To understand the importance of using TSH as a biological marker of thyroid health, we first must understand the hypothalamic-pituitary-thyroid (HPT) axis, a negative feedback loop for thyroid hormone regulation. The HPT axis begins in the brain, with the hypothalamus secreting a hormone called thyrotropin-releasing hormone (TRH) when it detects low concentrations of thyroid hormone in circulation. TRH signals the pituitary gland to release TSH into the bloodstream. TSH stimulates the production and release of thyroid hormones by the thyroid gland. As T3 and T4 levels increase in the blood, they exert negative feedback on the brain to inhibit the release of TRH and TSH, helping to maintain thyroid hormone levels within an optimal range. 

In essence, TSH acts as the thyroid's accelerator. When the thyroid needs to run faster (i.e., too little thyroid hormone in circulation), the pituitary steps on the gas, producing more TSH. When the thyroid needs to run slower (i.e., too much thyroid hormone in circulation), the pituitary eases off the gas, producing less TSH. Medical guidelines recommend measuring TSH to screen for thyroid dysfunction because it can indicate whether the thyroid is making too much or too little thyroid hormone.

High TSH Levels: Causes and Implications

In overt hypothyroidism, TSH levels are elevated, and free T4 levels are low. In subclinical hypothyroidism, TSH levels are elevated, and free T4 levels are normal. Hypothyroidism is divided into two categories: primary and secondary. (33) 

Primary hypothyroidism occurs when the thyroid gland cannot produce adequate thyroid hormone despite normal hormonal stimulation by the hypothalamus and pituitary. Secondary hypothyroidism is less common and occurs due to pathology related to the hypothalamus or the pituitary gland. (33) 

The most common cause of hypothyroidism worldwide is iodine deficiency. However, in iodine-sufficient regions (including the United States), Hashimoto's thyroiditis, an autoimmune thyroid disease (AITD), is the leading cause of hypothyroidism. Other common causes of hypothyroidism include medication, radioactive iodine therapy, and thyroid surgery. 

Symptoms of an elevated TSH may include: 

• Fatigue
• Unintentional weight gain
• Constipation
• Brain fog
• Cold intolerance
• Dry skin
• Hair loss and loss of the outer third of the eyebrow
• Depression
• Insomnia
• Joint and muscle pain
• Irregular and/or heavy menstrual cycles

Functional Medicine's Perspective on Elevated TSH

Unlike conventional medicine, which often focuses solely on symptom management and normalizing TSH levels through thyroid hormone replacement therapy, functional medicine looks at the whole patient, recognizing that health issues stem from complex interactions between genetics, lifestyle, environment, and emotional well-being. By adopting this holistic approach, functional medicine doctors explore the underlying factors contributing to elevated TSH, acknowledging that the thyroid gland doesn't operate in isolation but is intricately connected to the entire body's physiology.

Functional medicine providers' perspective on elevated TSH lies in investigating the root causes of thyroid imbalances. 90% of hypothyroidism is caused by autoimmunity, a condition in which the immune system mistakenly targets and attacks the body's cells, tissues, and organs. In the case of Hashimoto's thyroiditis, the immune system makes antibodies against thyroglobulin and/or thyroid peroxidase, impairing the thyroid's ability to make T3 and T4. The etiology of autoimmune disease is multifactorial, including genetic and environmental factors, such as environmental toxins, infection, stress, and intestinal dysbiosis and permeability. (5, 26) 

Additionally, diet influences TSH levels and thyroid health. Scientists believe a Western-style diet contributes to autoimmune disease due to the high intake of fat, sugar, and processed foods linked to many chronic inflammatory health conditions. Western diets also increase the risk of nutrient deficiencies; among others, B and D vitamin deficiencies are known to significantly and negatively impact thyroid functioning. Studies have also shown a strong link between AITD and gluten intolerance; in fact, patients with celiac disease have a four times increased risk of developing AITD. 

Functional medicine practitioners diligently explore these facets to pinpoint the specific factors contributing to an individual's elevated TSH, paving the way for targeted and personalized interventions. A distinguishing factor between the functional and conventional approaches to treating thyroid dysfunction is the use of optimal TSH levels in functional medicine. An ideal TSH can vary widely between individuals, depending on the person's age, gender, and symptomatic presentation. The standard reference range for TSH is based on the statistical distribution of TSH levels across the general population rather than according to the association of a TSH level with symptoms, adverse health outcomes, and disease risk. Most standard labs list normal TSH between 0.45-4.12 mIU/L. However, there is disagreement about the appropriate lower and upper normal limits for TSH and a growing consensus that a narrower range of 0.5-2.5 mIU/L may be more suitable for most healthy adults. This is why most functional medicine providers use this narrower reference range when interpreting thyroid lab results. (23, 36) 

Lab Testing for TSH and Other Thyroid Markers

While TSH is an important marker for screening thyroid function, relying on TSH alone could miss 7% of patients with thyroid dysfunction. This is why comprehensive thyroid testing is so important. Ordering a complete thyroid panel can provide better insight into the production and conversion processes of the HPT axis and highlight precisely where dysfunction occurs along the thyroid axis. In addition to TSH, functional medicine providers will commonly order the following tests: 

Total T3 and T4

‍Total T3 and total T4 measure the amount of bound and unbound thyroid hormones in the bloodstream. Total T3 and T4 represent the thyroid's ability to produce hormones but don't directly reflect the amount of biologically active hormones available to bind to receptors throughout the body. Total T3 and T4 will be reduced in hypothyroid cases stemming from a hormone synthesis problem. In healthy states, T4 is converted to T3 in peripheral sites, predominantly in the liver. Liver disease can result in poor thyroid hormone conversion and low total T3 levels. (6, 14, 41) 

Free T3 and T4

Free T3 and free T4 measure the unbound, biologically active form of thyroid hormones. The unbound portion of thyroid hormone is a more accurate indicator of thyroid influence on human physiology because it represents the portion available for conversion or exerting its effects at peripheral receptor sites. Total T3 and/or T4 may be normal, but if too much is bound, the free hormone will be low and hypothyroid symptoms can occur. For example, oral contraceptive pills, estrogen, pregnancy, liver disease, and hepatitis C viral infection can increase the amount of thyroid hormone-binding proteins, reducing free T3 and free T4 levels (42). (6, 14) 

Reverse T3

In times of illness, chronic stress, and nutritional deficiencies, T4 preferentially converts to reverse T3 over T3. Too much rT3 is a problem because it is largely biologically inactive and competes with T3 at receptor sites, leading to symptoms of hypothyroidism. (6, 14)

Thyroid Antibodies

Thyroid antibodies are diagnostic for thyroid autoimmunity. Thyroid peroxidase antibodies (TPOAb) target thyroid peroxidase, an enzyme involved in thyroid hormone synthesis. TPOAb is detected in over 80% of Hashimoto's cases. Thyroglobulin antibodies (TgAb) target the building block used to synthesize thyroid hormones and are present in over 50% of Hashimoto's patients. (14) 

Research indicates that up to 13% of healthy Americans have circulating thyroid antibodies, meaning that thyroid autoimmunity is diagnosable years before clinical symptoms and elevations in TSH manifest. Not only is the measurement of thyroid antibodies necessary to identify autoimmunity as the root cause of overt hypothyroidism, but it can also help screen for thyroid dysfunction before overt clinical disease develops. (6, 14) 

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Strategies to Address High TSH Levels Naturally

You've been diagnosed with high TSH levels. What's next? Your functional medicine provider will discuss integrative interventions to normalize thyroid hormone levels to an optimal value and palliate hypothyroid-related symptoms. While thyroid hormone replacement therapy may be necessary, many other natural treatment options support thyroid health. 

Diet for Thyroid Support

Researchers have extensively examined various dietary approaches aimed at enhancing thyroid health. Their findings indicate that various diets can benefit individuals with thyroid disorders. Customizing dietary adjustments according to an individual's medical history and personal preferences is crucial. We will explore a selection of diets that have demonstrated positive impacts on thyroid function, but it is worth highlighting that a common thread among all these dietary approaches is their focus on integrating nutrient-rich foods that supply the necessary nutrients for supporting thyroid hormone production and diminishing overall inflammation levels.

A healthy gut and liver are required for optimal thyroid function, and dysbiosis is common in thyroid disorders. Dysbiosis promotes inflammation, reduces immune tolerance, and can result in malabsorption of thyroid-specific vitamins and minerals. Supplemental probiotics have shown beneficial effects for treating thyroid disease. However, the gut microbiome can also be supported with a diet that emphasizes dietary intake of prebiotic and probiotic foods. (28) 

In one study, researchers investigated the relationship between dietary habits and oxidative stress markers in individuals with Hashimoto's thyroiditis. The findings reveal that adherence to a Mediterranean-like diet significantly reduces oxidative stress levels in patients and is correlated with lower rates of Hashimoto's disease. (35) 

A recent 2023 meta-analysis investigating the effects of a gluten-free diet on Hashimoto's thyroiditis concluded that gluten elimination results in positive clinical outcomes, including reductions in thyroid antibodies and TSH levels and increases in free T4 levels.

In a 2016 study, researchers assigned 180 people with Hashimoto's to a low-carbohydrate or low-calorie diet for weight loss. After 21 days, those on the low-carb diet experienced a drop in thyroid antibodies by at least 40%, whereas those following the low-calorie diet saw their thyroid antibodies rise. (22) 

Goitrogens are substances that can interfere with the normal functioning of the thyroid gland by blocking the uptake of iodine by the thyroid gland and inhibiting enzymes involved in thyroid hormone synthesis. Therefore, it may be beneficial to limit the consumption of goitrogenic foods, including cruciferous vegetables and soy products, to support thyroid function. (3)

Lifestyle Changes for Hypothyroidism

Establishing healthy lifestyle habits to support a healthy thyroid gland cannot be overstated. 

Stress disrupts the HPT axis by blunting TRH secretion and downregulating thyroid hormone production. Research shows that establishing a stress management routine improves thyroid function markers and symptoms of hypothyroidism. 

Sleep deprivation exacerbates stress levels and directly interferes with the HPT axis by altering TSH, T4, and T3 (32). Sleep apnea has also been associated with a higher prevalence and severity of thyroid autoimmunity. Good sleep hygiene refers to following established behaviors that help facilitate deep, restorative sleep. The following tips are recommended to support a healthy thyroid:

• Go to bed and wake up at the same time every day of the week
• Expose yourself to early morning light upon waking, and limit exposure to blue light in the evenings.
• Avoid intense exercise or stressful activities in the evening 
• Create a calm, quiet, and cool bedroom environment. Limit bedroom activities to sleep and sex, and keep computers, TVs, and work out of the room.
• Limit consumption of alcohol and caffeine, especially in the evenings. 

Regular physical activity can help alleviate symptoms of hypothyroidism, including fatigue, brain fog, weight gain, and depression, and reduce the risk of cardiovascular disease associated with low thyroid hormones. Studies also consistently show moderate-intensity aerobic exercise significantly decreases TSH and increases T3 and T4.

Supplements for Thyroid Health

Screening for and correcting identified nutrient deficiencies, including iodine, vitamin A, vitamin D, omega-3 fatty acids, and selenium, helps combat inflammation and ensures the thyroid has essential cofactors required for thyroid hormone production and conversion. (6) 

Selenium, in particular, plays an important role in optimizing thyroid health. As an antioxidant, selenium can reduce circulating thyroid antibodies by up to 63.6%, normalize thyroid hormone levels, and preserve the anatomical structure of the thyroid. (7, 12) 

Ashwagandha is an adaptogenic herb with anti-inflammatory, neuroprotective, immunomodulating, and stress-relieving properties that likely supports thyroid health and function. Preliminary evidence suggests taking 300 mg of ashwagandha root extract twice daily for eight weeks increases T3 and T4 and reduces TSH in patients with subclinical hypothyroidism. (15) 

Future Research on TSH and Thyroid Health

The landscape of thyroid health research is continuously expanding, with a growing understanding of the intricate complexities surrounding thyroid function and its impact on overall well-being. Connections between TSH and other health conditions, such as cardiovascular diseases, metabolic disorders, and mental health issues, are being recognized and explored. Ongoing research is investigating novel treatments, including nutrient therapy, herbal supplements, and stem cell therapy, as promising alternative treatment options to traditional hormone replacement therapy. This evolving comprehension paves the way for more precise diagnostics and targeted interventions, ensuring that healthcare approaches become increasingly personalized and effective.

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Summary

Recognizing the significance of understanding and addressing elevated TSH levels is paramount in ensuring optimal thyroid health. High TSH levels can signify underlying imbalances that require comprehensive evaluation and targeted intervention. Consulting with functional medicine practitioners is strongly encouraged for individuals seeking a holistic perspective on their thyroid health. These specialists search beyond traditional medical approaches, exploring the intricate web of factors contributing to thyroid imbalances. Functional medicine offers personalized and precise insights by considering the interconnectedness of genetics, lifestyle, diet, and environmental influences, fostering a more thorough understanding of thyroid health.