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Chronic Fatigue Syndrome and Thyroid Function

  [ 548 votes ]   [ Post a Comment ] • July 12, 2002

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The thyroid gland is the body's primary regulator of metabolism. Because it controls the body's metabolic rate - and the rate at which energy is produced, imbalances of thyroid hormones can have a profound effect on an individual's energy levels.

Hypothyroidism is one of the most common hormone disorders. It occurs with greater frequency in women between the ages of 40-50, and may affect as many as 10% of women over age 50.(1) In hypothyroidism, low levels of thyroid hormones T4 (thyroxine) and/or T3 (triiodothyronine) drastically slow the body's metabolic rate, causing fatigue and sleepiness, muscle weakness, and decreased blood flow.(2) At subclinical levels, imbalances may trigger vague complaints of persistent, low-grade fatigue; overt clinical hypothyroidism may be characterized by more extreme forms of exhaustion, as well as cognitive dysfunction, cold intolerance, weight gain, and constipation.

To compensate for low levels of T3 or T4, the pituitary gland may secrete higher amounts of thyroid stimulating hormone (TSH) in a futile attempt to "jump-start" the thyroid gland into producing more thyroid hormones.

In many cases, hypothyroidism arises in conjunction with chronic thyroid autoimmune responses. These responses may occur with chronic inflammation of the thyroid gland ("thyroiditis"). Over time, such a chronic inflammatory/immune response, signaled by elevated levels of thyroid autoantibodies, can cause the thyroid gland to deteriorate, eventually leading to thyroid hormone deficiencies. Even before this happens, high levels of thyroid antibodies, such as anti-thyroglobulin, may block thyroid hormones from attaching to cellular receptors, causing symptoms of hypothyroidism even when thyroid hormone levels are adequate.(3)

Vitamin and mineral deficiencies (like selenium, B2, and vitamin A), heavy metal toxicity, chronic stress, enzyme dysfunction, and aging can cause fatigue-inducing thyroid imbalances even when TSH and T4 levels remain normal. For example, if the body converts too much of T4 into the inactive form of T3, called reverse T3, the resulting reverse T3 dominance may interfere with the ability of T3, the most potent form of thyroid hormone, to gain access to cells.

Functional hypothryoidism is not the only thyroid imbalance that may deplete energy levels. If fatigue occurs as a result of chronic insomnia, nervousness, and weight loss, the problem may be high or excess levels of thyroid hormone levels, or hyperthyroidism. Subtle, subclinical imbalances in thyroid function, which may mimic symptoms of "classic" thyroid dysfunction without altering levels of conventional markers, underscore the importance of using a comprehensive evaluation of thyroid function to evaluate related conditions.

The Comprehensive Thyroid Assessment is a comprehensive analysis of thyroid hormone metabolism, including central thyroid gland regulation and activity, thyroid production and secretion, peripheral thyroid conversion, and thyroid autoimmunity. This test allows the practitioner to pinpoint common imbalances that underlie fatigue, which may go undetected with more limited assessments.

Comprehensive Thyroid Assessment

The Comprehensive Thyroid Assessment is a thorough analysis of thyroid hormone metabolism, including central thyroid gland regulation and activity, thyroid production and secretion, peripheral thyroid conversion, and thyroid autoimmunity. This test allows the practitioner to pinpoint common imbalances that underlie a broad spectrum of chronic illness.

Thyroid hormones are essential and primary regulators of the body's metabolism. Imbalances can affect virtually every metabolic process in the body, exerting significant effects on mood and energy level. Thyroid function has a profound impact on overall health via its modulation of carbohydrate, protein, and fat metabolism, vitamin utilization, mitochondrial function, digestive process, muscle and nerve activity, blood flow, oxygen utilization, hormone secretion, sexual and reproductive health, and many other physiological parameters.

One of the most common hormonal disorders, hypothyroidism has been called the "great imitator" for the vast number of medical conditions it can mimic. Thyroid imbalances may elicit fatigue, depression, coldness, constipation, poor skin, headaches, PMS, dysmenorrhea, fluid retention, weight gain, anxiety/panic attacks, decreased memory and concentration, muscle and joint pain, and low sex drive.

The Comprehensive Thyroid Assessment reveals imbalances that often go undetected with more limited assessments. Unbound levels of T4 and T3 are measured to reflect the bioactive portion of thyroid hormone, increasing clinical insight. This assessment can identify not only overt hyper- and hypothyroidism, but subtle sub-clinical manifestations of thyroid dysfunction, such as auto-immune reactions and altered peripheral conversion into T3 leading to reverse T3 dominance. These metabolic anomalies may trigger chronic symptoms, and promote the gradual development of degenerative disorders.

The Comprehensive Thyroid Assessment can detect metabolic irregularities arising from vitamin and mineral deficiencies, heavy metal toxicity, chronic stress, enzyme dysfunction, and aging even when TSH and T4 levels are normal. Thyroid antibody levels help gauge autoimmune response frequently associated with antigenic cross-reactivity and gastrointestinal dysfunction, which may require additional clinical investigation and focused intervention. Thyroid antibody levels may rise in response to trauma, dysbiosis, inflammation (including thyroiditis) and progressive thyroid degeneration. At high levels, antibodies may block thyroid hormones from attaching to cellular receptors, causing symptoms of hypothyroidism even when thyroid hormone levels are adequate.

Ensuring healthy thyroid function is a valuable tool in preventive medicine. Optimal thyroid function may help safeguard against the pathogenesis of diabetes, obesity, heart disease, and depression. Thyroid hormones also play central metabolic roles in healthy sexual and reproductive function in both women and men. Because they are essential for IGF-1 production, thyroid hormones significantly affect lipid metabolism.

What You Should Know

This test may reveal important clinical information about:

- Central thyroid dysregulation indicating primary or secondary thyroid disease or dysfunction, associated with fatigue, depression, coldness, hair loss, headaches, PMS, menstrual irregularities, fluid retention, unexplained weight gain or weight loss, anxiety or panic attacks, decreased memory or concentration, muscle and joint pain, low libido, and infertility

- Peripheral thyroid imbalances arising from nutrient shortages, heavy metal exposure, adrenal stress, enzyme deficiencies, and other chronic illness, which may result in functional hypothyroidism, known variously as euthyroid sick syndrome (ESS), low T3 syndrome, or Wilson's syndrome

- Thyroid antibody levels, to gauge autoimmune response that can interfere with thyroid receptor function and promote inflammatory diseases like Hashimoto's thyroiditis, Graves' disease, or postpartum thyroiditis.


1 Elliot B. Diagnosing and treating hypothyroidism. Nurse Pract 2000;25(3):92-4,99-105.

2 Guyton AC. The thyroid hormones. In: Textbook of Medical Physiology, 6th ed. Philadelphia: WB Saunders;1982:940.

3 Vliet EL. Screaming to be heard: hormonal connections women suspect and doctors ignore. New York: M Evans & Co, 1995;59.

Source: Genova Diagnostics (formerly Great Smokies Diagnostic Laboratory).

For more information, visit Genova Diagnostics at

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