Hyperactivity of the thyroid gland is called hyperthyroidism. This hyperactivity causes excess hormone secretion by either the whole gland or a part of the gland that has become overactive for some reason. The thyroid glad can become hyperactive for various reasons.
The most common reason reason for hyperthyroidism is Graves’ disease. This is an autoimmune condition, in which the body starts producing antibodies to destroy a part of itself. In this case, the antibodies are formed against the thyroid gland. In this condition the gland becomes hyperactive, to the extent where it forms a goiter (an abnormally enlarged gland). This is noticeable as a large swelling in the neck. As a result it produces large amounts of hormone, which are released into the blood. This hyperactivity is caused by the binding of auto antibodies to certain parts of the gland, destroying it. The disease is thought to be triggered by factors such as, stress, smoking, radiation to the neck, medications and organisms such as viruses.
The symptoms of Graves’ disease are varied and involve the gland itself; inflammation and swelling of tissues around the eyes, causing the eyes to bulge out in severe cases; and thickening of the skin on the lower legs, known as pretibial myxedema. The cause of this disease is not known; however, it tends to be familial or hereditary. Patients who have this disease may also have a family history of other diseases, such as diabetes and arthritis.
As opposed to Graves’ disease, which involves the entire gland, the hyperactivity of the thyoird can be restricted to a specific part of the gland. This is known as a nodule. The nodule is usually a non-cancerous tumor in the gland. Sometimes it produces large amounts of thyroid hormone. The nodules are said to be either hot or cold. A hot nodule produces excessive amounts of thyroid hormone. A cold nodule does not produce any hormone.
Another cause of hyperthyroidism is thyroiditis. There are different types of thyroiditis, which cause inflammation of the thyroid and other symptoms. Some are painful, and others painless. The causes of thyroiditis include autoimmune disease, bacteria, viruses, radioactive treatment and certain drugs. Hyperthyroidism caused by thyroiditis produces symptoms such as anxiety, insomnia, palpitations (a fast heart rate), fatigue, weight loss and irritability. These symptoms usually resolve when the stores of hormone in the thyroid are depleted. Additionally, several treatment alternatives are available to correct this condition.
Another less common cause of hyperthyroidism involves the intake of thyroid hormones for a long time, especially T3 hormone.
Hyperthyroidism is also a result of any abnormality causing increased production of thyroid stimulating hormone (TSH) from the pituitary gland in the brain. A pituitary tumor may cause abnormal amounts of TSH to be released in the blood.
Iodine is an important constituent of thyroid hormones; therefore, excessive intake of iodine can also cause production of large amounts of thyroid hormone.