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Hyperthyroidism : Causes
Western Medicine Chinese Medicine
There can be several causes for hyperthyroidism, but the most common are:

Graves' disease
toxic nodular goiter, and
toxic adenoma.

Graves' disease

Graves' disease, or primary toxic goiter, is the most common form of hyperthyroidism and accounts for 75 per cent of cases of thyrotoxicosis. It is an autoimmune disease in which antibodies produced by the immune system attach to specific sites on the thyroid gland and stimulate the gland to produce excess amounts of thyroid hormones. In the majority of patients this over-stimulation of the thyroid results in diffuse enlargement of the gland, a condition known as a goiter. The goiter can be two to three times the size of the normal gland and is accompanied by an increased blood flow. Diffuse goiters are only seen in Graves' disease and are more common in younger patients.

Enlarged thyroid gland in Graves' disease

Toxic nodular goiter

This form of hyperthyroidism occurs in 15 to 20 per cent of cases and tends to affect the older age group. Instead of the entire thyroid gland being enlarged, as in Graves' disease, abnormal growth occurs in multiple nodules. These nodules comprise thyroid cells that have lost their regulatory mechanism and secrete an excess of thyroid hormone. Thyroid nodules are found in four per cent of all adults, although individuals may be unaware of them, and again are more common in women.

Thyroid gland in toxic nodular goiter

Toxic adenoma

When nodular growth in the thyroid gland presents as a single lump, it is called a toxic adenoma and is commonly referred to as a "hot" nodule because of its hyperactivity. The condition accounts for less than five per cent of all cases of hyperthyroidism. The nodule is a benign (non-cancerous) tumor that secretes excess thyroid hormones and inhibits TSH secretion. This results in diminished function in the rest of the gland. Toxic adenoma tends to occur in women over the age of 40 years. The tumor is often more than 3 cm in size, but the symptoms of hyperthyroidism it generates are usually mild.

Thyroid gland in toxic adenoma

Other causes
Less common causes of hyperthyroidism include:

Subacute thyroiditis. Painful inflammation of the thyroid gland by a virus induces a sudden release of thyroid hormones into the circulation.
Postpartum thyroiditis. Temporary disturbances of thyroid function occur in five to 10 per cent of women within six months following childbirth. The condition is painless.
Iodine-induced hyperthyroidism. Occasionally the administration of iodine in contrast media and the drug amiodarone (used for regulating heart rhythm) can result in hyperthyroidism. The disease is usually mild and self-limiting.
Pituitary tumor. Very rarely a TSH-producing pituitary tumor (a malignant growth of the pituitary gland) increases secretion of thyroid hormones.
Click here to see the causes of Hyperthyroidism from a TCM perspective

In identifying the causes of hyperthyroidism, most TCM physicians believe that when those individuals who are prone to a natural deficiency of yin encounter emotional problems, such as anxiety or anger, stagnation of liver-qi occurs. This generates fire evil and causes further drying up of the body's yin and blood. The liver then fails to perform its regulatory role for other organs, such as enhancing the digestive properties of the spleen.

If an individual is deficient in both liver-yin and kidney-yin, the body is then more likely to create phlegm evil. The phlegm evil obstructs the meridians causing an erratic qi circulation. When stagnant qi and phlegm evil collect in region of the neck, they give rise to goiter formation.

For a long time, TCM practitioners have believed that emotional and spiritual factors have a great influence on hyperthyroidism and result in a number of hyperthyroid-related symptoms:

Over-stimulation by the seven modes of emotions leads to under-functioning of the liver and a failure in its regulation of the qi circulation. When too much qi is flushed up to the head, individuals become impulsive and irritable. They develop flushing of the face, blood-shot eyes, a bitter taste in the mouth, a dry throat, dizziness and vertigo.
Emotional problems cause liver-qi stagnation and this generates fire evil. The fire evil damages the stomach, producing an increase in appetite and a persistent feeling of hunger.
When qi flow in the spleen is disrupted, the digestive system is affected. Poor digestion and absorption result in weight loss and fatigue.
Impaired function of the liver also affects the flush channel and the storage of blood. Amenorrhea (absence of periods) and irregular or scanty menstruation can follow.
Deficiency of yin leads to hyperactivity of the prime minister-fire. This creates a condition where a virtual fire burns inside the kidneys causing nocturnal emission of semen and impotence.
Deficiency of yin leads also to a failure of the kidneys to nourish the liver. Liver-yang becomes hyperactive and generates wind evil; this can cause hand tremor. Tremor or stiffening of the tongue may also occur. This abnormal state results mainly from endogenous wind evil and is also seen in alcoholism.
Yin-deficiency in the heart and kidneys leads to palpitation, sweating, insomnia and nightmares.
Yin-deficiency creates a virtual fire inside the body and individuals develop an aversion to heat. On examination, the tongue is generally red and the pulse is fine and rapid.