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  • Writer's pictureDr. Teresa Rispoli

Optimize Thyroid Health Naturally: Understanding Symptoms Beyond T4 & TSH Tests

Thyroid exam

Thyroid hormones influence nearly every organ system in the body, encompassing the heart, central nervous system, autonomic nervous system, skeletal structure, gastrointestinal tract, and metabolism. So optimal function is essential.

Thyroid symptoms can vary between individuals and can include:

  • Fatigue

  • Occasional constipation

  • Weight gain, difficulty losing weight

  • Intolerance to cold, cold hands and feet

  • Dry skin

  • Dry, thinning hair or hair loss

  • Mood concerns

  • Joint and muscle discomfort

  • Heavy or irregular menstrual cycles, fertility concerns

  • Slowed heart rate

  • Low libido


Four hormones have been identified to be secreted by the thyroid, T1, T2, T3, and T4. The two primary hormones are thyroxine (T4), a prohormone, and triiodothyronine (T3), which is 300 times more biologically active than T4.

Successful conversion of T4 to T3 relies heavily on transport proteins, along with nuclear receptors and selenium-dependent enzymes known as deiodinases. These three players are crucial to homeostasis at the cellular level as they coordinate the uptake, activation and deactivation of thyroid hormone within the cell.5 Conversion of T4 to T3 occurs primarily in the liver and kidneys, but also within the gut, bones, muscles, adipose tissue, heart and CNS.6, 7, 8 INHIBITORS OF T4 TO T3 CONVERSION

Eighty percent of the T3 found in circulation is produced by peripheral conversion from T4.4 A number of lifestyle, environmental, and dietary factors can inhibit this conversion and lead to symptoms.4, 9, 10, 11, 12 T4 to T3 conversion influences all tissues within the body, as they are dependent on T3 for normal cell function.

Inhibitors of thyroid conversion


In line with standard practices, practitioners commonly rely on TSH and T4 levels to screen for thyroid concerns. While these markers play important roles, they don’t tell the whole story. Getting to the root of an individual’s symptoms requires investigating what is occurring further down the thyroid hormone pathway at the cellular level, and why. This begins with understanding that although TSH and T4 levels can provide insight into thyroid gland function, they don’t reflect:

  • Alterations in cellular sensitivity to thyroid hormones

  • Inadequate peripheral conversion of inactive T4 to metabolically active T3

  • Poor uptake of thyroid hormones into the mitochondria

  • Activity of rT3, anti-thyroid antibodies or environmental factors which can displace thyroid hormones and prevent their binding to cellular receptors.

Any one of these factors along with impaired T4 to T3 conversion, or fluctuation in T3 and rT3 levels can trigger changes in an individual long before TSH or T4 are outside their respective reference ranges.

Expanding the assessment of thyroid function beyond TSH and T4 can provide insight into what is happening peripherally to T4.

The following markers can provide evidence of suboptimal thyroid function:


Measuring total thyroid hormones provides the sum of both the free thyroid hormone and thyroid hormone bound to a protein; however, it does not differentiate how much of that hormone is available for uptake by the cells. A hormone bound to a protein is inactive. Only the free T4 and free T3 tests measure the levels of thyroid hormones in circulation that are available to cells.


rT3 can be produced in response to physical or emotional stress. Free T3 and rT3 can both bind to thyroid receptors on the cell. When rT3 binds to thyroid receptors, it inactivates them and prevents the metabolically active hormone T3 from binding to receptors.


Thyroid peroxidase antibodies (TPO antibodies) and thyroglobulin antibodies (TG antibodies) can be produced when the body begins to lose “self-tolerance”. Thyroid antibodies can be present long before aberrations are seen in TSH and T4.


Elevated urinary cortisol metabolites have been associated with diminished peripheral thyroid hormone metabolism.14 Examining the role stress plays in thyroid function in each client is foundational for any thyroid care plan by a Functional Nutritionist.


Various nutrients participate in the synthesis, metabolism, and mechanisms of action of thyroid hormones in order to optimize thyroid health naturally.

Curcumin helps to neutralize free radicals that may affect iodothyronine 5’-monodeiodinase enzyme activity, the limiting factor in the conversion of T4 to the more active T3 hormone.14

Vitamins A and D help to maintain healthy thyroid cell metabolism and support triiodothyronine (T3) and thyroxine (T4) hormone function.15, 16

Ashwagandha helps maintain healthy thyroid function and relaxation as suggested in preliminary research.17

Forskolin in coleus extract has been shown to support thyroid hormone metabolism in preclinical models, potentially by promoting adenylate cyclase activity.

Zinc and Selenium help to maintain healthy thyroid cell metabolism and support triiodothyronine (T3) and thyroxine (T4) hormone function.19, 20 Selenium has also been shown to help to neutralize free radicals that may affect iodothyronine 5’-monodeiodinase enzyme activity, the limiting factor in the conversion of T4 to the more active T3 hormone.13

Probiotics support healthy intestinal microflora to promote digestive and immune health.


Thyrotain includes a multidimensional blend of nutrients and botanicals to help maintain healthy thyroid function. Clinical Applications

  • Helps to Maintain Healthy Thyroid Function

  • Promotes the Synthesis of Thyroid Hormones

  • Helps Support Conversion of T4 to T3

  • Improves Cellular Sensitivity to Thyroid Hormones

  • Supports a Healthy Inflammatory and Antioxidant Balance

Thyrotain is a comprehensive formulation that provides a blend of nutrients and botanicals working in synergy to support thyroid health. Thyrotain includes L-tyrosine and iodine, which make up the backbone of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). The addition of zinc, selenium, vitamin A, and the botanical guggulipid activate enzymes that enhance the conversion of T4 into the active thyroid hormone T3. Vitamin A and zinc also help improve cellular sensitivity to thyroid hormones. Turmeric, along with the antioxidants vitamin C and E and N-acetyl cysteine (NAC), provide a powerful combination of antioxidants that boost thyroid health by reducing free radical stress.

Suggested Use:

4 capsules per day or as recommended by your health care professional. The above information is intenden for educational purposes. Get The Whole Picture by Getting a Complete Thyroid Panel I recommend you be evaluated with a Functional Nutritionist like myself who is educated in thyroid health using a functional approach. Conventional doctors only look at TSH & T3 because they are not taught in the nutritionalaspects of balancing the thyroid. Whereas Functional Nutritionists will perform a Complete Thyroid Panel so they can take a look at the other factors influencing your thyroid and recommend the appropriate diet, lifestyle and supplement therapy to bring your thyroid back into balance without medicine.

Dr. Teresa Rispoli, ND. DCN, LAC

Dr. Teresa Rispoli, DCN, L.Ac.,


30 Years in Holistic Health & Beauty! 

If you are looking to have more energy, better brain function, focus, performance, endurance, or want to optimize your hormones with natural approaches then you are in the right place. If you need help with your health, have gut issues; SIBO, Leaky Gut, Candida, IBS, immune system, Autoimmune issues, or skin disorders, Dr. Rispoli is highly trained and skilled in Functional Medicine, and holistic approaches to healing. 

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Dr. Teresa Rispoli,
PhD., ND, LAc.

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