Thyroid disease occurs when the thyroid gland, located in the neck, is not functioning properly. The thyroid produces and releases two hormones, thyroxine (T4) and triiodothyronine (T3), which regulate the body's metabolism (the rate at which essential reactions are performed). Approximately 20 million Americans suffer from some form of thyroid disease, according to the Cleveland Clinic, so it is important to know what can cause the disease.
Inflammation
Thyroiditis is the general term used to describe conditions characterized by inflammation of the thyroid gland. Some of the conditions that cause inflammation of the thyroid destroy the cells of the thyroid slowly, resulting in hypothyroidism (low levels of thyroid hormone). Other conditions destroy the cells in the thyroid rapidly, causing all the stored thyroid hormones to be released at once, resulting in thyrotoxicosis. The symptoms of thyrotoxicosis are similar to hyperthyroidism including anxiety, insomnia, increased heart rate, fatigue and weight loss.
Hashimoto's thyroiditis, the most common cause of hypothyroidism, according to the American Thyroid Association, occurs when the cells of the body's immune system attack the cells of the thyroid gland. The cells of the thyroid are destroyed, leaving the body with deficient levels of thyroid hormone. In response, the pituitary gland, which produces thyroid stimulating hormone (TSH), produces more TSH to stimulate the thyroid to produce more thyroid hormones. This results in severe inflammation of the thyroid, known as a goiter.
Post-partum thyroiditis causes inflammation of the thyroid, which results in thyrotoxicosis followed by a phase of hypothyroidism. This condition is usually temporary with approximately 80 percent of patients returning to a normal thyroid function within 12 to 18 months as reported by the American Thyroid Association.
Iodine Deficiency
The cells of the thyroid gland are the only cells in the body that can absorb iodine. Iodine is necessary for the production of thyroid hormones. Although iodine deficiency is rare, according to the Merck Manual, it can result in thyroid disease. When there is not enough iodine present, the thyroid gland enlarges to absorb more iodine. The resulting goiter is not able to produce enough thyroid hormone, resulting in hypothyroidism.
Thyroid Cancer
Thyroid cancer is the abnormal growth of cells in the thyroid, causing a tumor. There are four types of thyroid cancer, each of which can cause thyroid disease. Papillary thyroid cancer accounts for 80 percent of all the thyroid cancer cases, according to the National Cancer Institute. The second most common type is follicular thyroid cancer, followed by medullary thyroid cancer and anaplastic thyroid cancer.
Pituitary Tumors
The pituitary gland, located at the base of the brain, produces thyroid stimulating hormone (TSH), which regulates the production of the thyroid hormones within the thyroid gland. The presence of an adenoma, a noncancerous tumor, in the pituitary can interfere with the production of TSH. The tumor may stimulate an overproduction of TSH, resulting in hyperthyroidism, or it may inhibit the production of TSH, resulting in hypothyroidism.
