Thyroid Dysfunction

The thyroid gland is a key part of the endocrine system that produces hormones to regulate metabolism and growth. In traditional Chinese medicine, thyroid problems are generally described in terms of swelling, without specifying whether the condition is hyper- or hypothyroid. These problems are grouped into three categories: goiter and thyroid swelling without systemic symptoms, hyperfunction with heat and/or yin deficiency (with or without swelling), and hypofunction with cold and yang deficiency (with or without swelling).

Biomedical View of Thyroid Physiology

The thyroid gland is a key organ in the endocrine system, producing hormones that regulate metabolism and growth. It produces two main hormones, thyroxine (T4) and tri-iodothyronine (T3), which are released into the bloodstream and affect the metabolism of cells throughout the body. The production of these hormones is regulated by the thyroid stimulating hormone (TSH) produced by the pituitary gland in response to stimuli such as cold temperatures or stress. Adequate dietary iodine is required for the synthesis of thyroid hormones.

Hyperthyroidism can be treated with antithyroid drugs that block the production of thyroxine by inhibiting enzymes involved in thyroid hormone production. Common drugs in this class include thionamides such as carbimazole, methimazole, and propylthiouracil. These drugs are often the first line of treatment for thyroid dysfunction. However, they can cause the gland to increase in size due to stimulation of TSH by the pituitary gland, especially at high doses. More than half of people who use these drugs experience a relapse within two years of stopping treatment, likely because the underlying causes of their thyroid dysfunction are not addressed.

Radiation therapy using radioactive iodine is another treatment option for hyperthyroidism. The radioactive iodine is taken up by and concentrated in the thyroid gland, where it destroys a portion of the gland's tissue. This treatment is usually only given to people who are past reproductive age, as radiation can cause birth defects. One drawback of using radioactive iodine is that it can be difficult to calculate the right dose to reduce thyroid gland activity without destroying it completely. As a result, many people who receive this treatment end up with hypothyroidism and need to take exogenous thyroxine hormones.

Treatment of hypothyroidism typically involves hormone replacement therapy with synthetic thyroxine, which is available under various trade names. These medications are designed to mimic the effects of naturally-occurring thyroxine hormones. In some cases, treatment may involve using a product made from the ground-up thyroid gland of animals. These products contain natural thyroid hormones and are used to replace missing hormones in the body. The dosage of hormone replacement therapy is typically adjusted based on laboratory test results, but it is important to note that progress should not be solely determined by lab results. Some people may experience improvements without significant changes in hormone levels.

Causes

The thyroid gland is a crucial part of the endocrine system, producing hormones that regulate metabolism and growth. In traditional Chinese medicine, its health is influenced by the liver, spleen, heart, and kidneys. Pathological processes in the thyroid often affect the liver-spleen and heart-kidney axes, which are essential for proper functioning and reproduction. Dysfunction in the thyroid can lead to swelling, known as "ying bing," and can be grouped into three categories: goiter, hyperfunction with heat and/or yin deficiency, and hypofunction with cold and yang deficiency.

Phlegm

In traditional Chinese medicine, phlegm is often present when the thyroid gland swells and causes nodules or goiter. This phlegm is a result of a disrupted fluid metabolism, which can be caused by weakness in the spleen, lungs, and kidneys, yin deficiency, or liver qi constraint. Phlegm can contribute to further qi blockage, generate heat, or be complicated by static blood. It tends to affect the liver channel and can be concentrated in the neck in cases of heat, or diffuse in cases of cold and yang deficiency, causing symptoms such as myxedema, hoarse voice, or high cholesterol and triglycerides.

Constitution

A tendency towards thyroid disorders can be inherited, with hyperthyroidism having a particularly strong genetic component. The development of the disorder is influenced by weakness in one of the two major organ axes. The most common factor is weakness of the kidneys and source qi, which predisposes to disruption of the heart-kidney axis and to invasion by external pathogens. This weakness also affects the function of the penetrating and conception vessels, leading to pathological accumulation along their pathways in the neck.

Environment

Populations living in areas with low levels of iodine in the soil, such as mountainous regions, are more likely to develop goiter. Dry, desiccating environments can damage kidney yin and fluids, leading to the development of yang deficiency, which is further exacerbated by a cold, goitrogenic, or inadequate diet.

Diet

Aspects of the diet can influence the development of thyroid problems. A low iodine diet can cause poor thyroid function, and a diet rich in goitrogenic foods can inhibit thyroid function. Cold, raw foods that weaken the spleen can lead to dampness and phlegm or weaken yang qi, while a heating diet can contribute to an inflammatory tendency. Selenium is an important trace element for normal thyroid function and is often low in many soils. A gluten-free diet may be helpful in people with suspected gluten intolerance/celiac disease and thyroid disorder. Compromised spleen function can contribute to dampness and phlegm, leading to qi deficiency and susceptibility to infection that can trigger thyroid pathology.

Shock and Emotional Trauma

It is observed that the onset of hyperthyroidism (most commonly) or hypothyroidism sometimes follows major trauma, usually a few months after the event. This type of trauma disrupts the Heart-Kidney axis. This kind of trauma is different from the everyday stresses and frustrations that accumulate to cause Liver qi constraint.

Chemicals and Drugs

Some drugs, such as amiodarone, can influence thyroid function, especially those that contain high amounts of iodine. Iodine in large doses can cause both hyperthyroidism and hypothyroidism. Lithium carbonate, dopamine, and glucocorticoids can inhibit thyroid hormone production, while beta blockers and other drugs can inhibit the conversion of T4 to T3. Industrial and environmental chemicals, such as polychlorinated biphenyls and bisphenol-A, can interfere with the thyroid by binding to thyroid receptors and inhibiting iodine uptake.

Treatment

Chinese medical treatment of thyroid disorders focuses on correcting imbalances that led to the disorder, rather than just addressing thyroid function. This approach is often successful, especially when treatment is started early on, and can prevent recurrences. Common underlying pathologies, such as Heart-Kidney axis disruption, respond well to treatment. Heat must be quickly dealt with to avoid further complications. For mild to moderate conditions, herbal prescriptions can be used to target the underlying pathology, while antithyroid medications can be reduced or discontinued. Treatment of hypothyroidism is more complicated, but rebuilding qi and yang can compensate for many symptoms.