The thyroid gland is a butterfly-shaped endocrine gland found below the skin in the frontal part of the neck. It produces thyroid hormones, which control the speed at which many body processes, such as heartbeat, occur. The thyroid gland can be affected by a group of diseases that inhibit or impair the function of the gland.
Hyperthyroidism
Hyperthyroidism is a thyroid disease characterized by overproduction of thyroid hormones. According to the Merck Manuals Online Medical Library, its causes include Graves' disease, thyroiditis, exposure to radiation, toxic thyroid nodules and overstimulation of the thyroid gland by pituitary hormones.
Hyperthyroidism speeds up the rate of body processes, such as heart rate. Signs and symptoms of this thyroid disease include weight loss regardless of increased appetite, intolerance to heat, an enlarged thyroid gland, increased heart rate, anxiety and nervousness, abnormal heart rhythms, increased level of activity even though a person is tired, shakiness and difficulty sleeping.
Hypothyroidism
Hypothyroidism is when the thyroid gland does not produce sufficient amounts of thyroid hormones, according to Cleveland Clinic. When this happens the body processes progress slower than normal. Causes of this hormonal disorder include Hashimoto's thyroiditis--the most common cause of hypothyroidism--silent lymphocytic thyroiditis, subacute thyroiditis, surgical removal of the thyroid gland, exposure to radiation therapy used in hyperthyroidism treatment, inherited diseases and a diet deficient in iodine. Some signs of this condition are slow speech, a hoarse voice, dull facial expressions, weight gain and the inability to tolerate cold temperatures.
Thyroid Cancer
The American Thyroid Association explains that when compared with other cancers that affect endocrine glands--hormone-secreting organs--thyroid cancer is the most common. It is a rare form of cancer when compared with all other types of cancer. The exact cause of thyroid cancer is not known but it is common in people whose neck, chest or head were exposed to radiation during childhood. A sign of thyroid cancer is a lump in the neck called a thyroid nodule. The nodule may or may not impair thyroid function. However, the Hormone Foundation explains that some nodules may cause oversecretion of thyroid hormones.
Diagnosis
Secretion of thyroid hormones depend on TSH, or thyroid stimulating hormone--a hormone released by the pituitary gland. When TSH is released, it makes the thyroid gland secrete thyroid hormones. Blood tests that measure the amount of TSH along with any symptoms are used to diagnose hyperthyroidism or hypothyroidism. Thyroid cancer is diagnosed by aspirating a sample of any nodules present in the thyroid gland and then examining them under a microscope.
References
- Cleveland Clinic: Thyroid Disease
- The Hormone Foundation: Thyroid Disorders Overview
- American Thyroid Association: Cancer of the Thyroid
- Merck Manuals Online Medical Library: Thyroid Gland Disoders
- "Diseases and Disorders"; Victoria J. Fraser; 2007
