Thyroid disorders


Hormonal disorders or endocrine disorders, including thyroid disorders, are illnesses that occur when the body releases too many or too few hormones. Hormones are chemicals messengers that are released into the bloodstream. Hormones send messages to cells throughout the body in order to regulate bodily functions, such as growth, metabolism, and sexual development. As a result, individuals with hormonal disorders experience a disruption in such bodily functions.
Thyroid disorders are among the most common medical conditions but, because their symptoms often appear gradually over time, they are commonly misdiagnosed. There are four main types of thyroid disease: hyperthyroidism or too much thyroid hormone; hypothyroidism or too little thyroid hormone; benign (non-cancerous) thyroid disease; and thyroid cancer.
The thyroid gland is a small, butterfly-shaped gland located in the base of the neck on both sides of the lower part of the voice box (larynx) and upper part of the wind pipe (trachea). The thyroid produces hormones, called thyroxine (T4) and triiodothyronine (T3), which affect the body's metabolism and energy level. Thyroid hormone is also produced in response to thyroid stimulating hormone (TSH, also known as thyrotropin) secreted by the pituitary gland.
Release of thyroid hormones is controlled by the hypothalamus and pituitary gland, both found deep inside the brain. One of the most important features of the endocrine system is its regulation (control) by negative feedback. This means that the glands that stimulate the release of a hormone (for example, the pituitary) from another gland (for example, the thyroid) are eventually shut off, in a sense, so that too much hormone is not produced.
Thyroid disorders affect some 4.5 million Americans. At least 600,000 of them have yet to be diagnosed.

Related Terms

Arrhythmias, autoimmune, benign, biopsy, bradycardia, cancerous, cretinism, De Quervain's thyroiditis, diabetes mellitus, exophthalmia, exophthalmos, FANA, fluorescent antinuclear antibody test, goiter, Graves' disease, Graves' ophthalmopathy, hyperparathyroidism, hyperthyroid, hyperthyroidism, hypocalcemia, hypoparathyroidism, hypothyroidism, IGT, impaired glucose tolerance, intrinsic factor, iodine, malignant, myxedema, non-cancerous, nuclear scan, osteoporosis, parathyroid, parathyroid hormone, pernicious anemia, PTH, subclinical hyperthyroidism, subclinical hypothyroidism, tachycardia, tetany, thyroid storm, thyroidectomy, thyroiditis, thyrotoxicosis, ultrasound, vitamin B12, vitiligo.

types of thyroid disorders

Hyperthyroidism: Hyperthyroidism occurs when the thyroid gland produces too much thyroxine. As a result, the individual's metabolism increases dramatically, leading to weight loss and irregular heartbeat.
Most individuals fully recover from hyperthyroidism with treatment. However, if left untreated, the condition may be life threatening. Complications may include heart problems, brittle bones, and thyrotoxic crisis (sudden release of thyroid hormone). Thyrotoxic crisis occurs when symptoms suddenly become extreme, causing fever, increased heartbeat, and sometimes delirium.
The most common cause of hyperthyroidism is Grave's disease. In Graves' disease, a malfunction in the body's immune system releases abnormal antibodies that mimic thyroid stimulating hormone (TSH). Spurred by these false signals to produce, the thyroid's hormone factories work overtime and produce an excess of thyroid hormone.
Exophthalmia, also known as exophthalmos, is bulging of the eyes. Exophthalmia is a characteristic of individuals with Grave's disease. Exophthalmia occurs in about 40-60% of individuals who suffer from Grave's disease.
Non-cancerous tumors (abnormal growths) on the thyroid gland may also lead to hyperthyroidism. Some tumors may cause the thyroid to produce excess thyroid hormone. This causes the thyroid to become enlarged.
Hyperthyroidism may also occur if the thyroid gland becomes inflamed, called thyroiditis. When the gland is swollen, stored thyroid hormone may leak into the bloodstream.
Hypothyroidism: Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormone.
A condition called Hashimoto's thyroiditis is the most common cause of hypothyroidism in the United States. Thyroiditis is an inflammation of the thyroid gland not due to infection. Several types of thyroiditis exist and the treatment is different for each. Hashimoto's thyroiditis occurs when the individual's immune system attacks the thyroid gland, causing low levels of thyroid hormone. Researchers have not discovered why the immune system mistakes the thyroid for a harmful invader, such as a virus. It has been suggested that many factors lead to the disorder, including age, heredity, and gender. This is because the condition is most common among middle-aged women. It also common among biological family members.
Other less common types of hypothyroidism include De Quervain's thyroiditis and silent thyroiditis. In De Quervain's thyroiditis, the thyroid gland generally swells rapidly and is very painful and tender. In silent thyroiditis, there is no pain or needle biopsy (removal of tissue for examination).
Hypothyroidism may also occur if individuals do not consume enough iodine in the diet. This is most common in poor countries where malnutrition is common. Iodine is an essential element that helps the thyroid gland produce hormones.
A goiter is an enlargement of the thyroid gland. Although generally not uncomfortable, goiter can interfere with swallowing or breathing. Goiters are more common in women and older adults. The most common cause of goiter is a shortage of iodine in the diet in areas where the soil is deficient in iodine. Although goiters generally do not cause pain, a large goiter may interfere with swallowing or breathing and it may affect the individual's appearance and self-esteem. In many cases, goiters will be cured once hormone replacement therapy is started. However, some individuals may need to have their goiter surgically removed. Goiters are typical of hypothyroidism.
Individuals should visit their healthcare providers every six to 12 months to monitor their hormone levels. Over time, the dosage of thyroid medication may need to be changed. If the dose is too high, individuals may develop a condition called osteoporosis, which causes the bones to become hollow and brittle. Also, excessive doses may lead to irregular heartbeats (arrhythmias). In order to prevent complications of overdose, individuals with a history of heart disease, osteoporosis, or severe hypothyroidism may receive smaller doses that are gradually increased over time.
Thyroid nodules: Thyroid nodules are lumps that commonly arise within an otherwise normal thyroid gland. Often these abnormal growths of thyroid tissue are located at the edge of the thyroid gland so they can be felt as a lump in the throat. When they are large or when they occur in very thin individuals, they can even sometimes be seen as a lump in the front of the neck. One in 12-15 young women has a thyroid nodule, and one in 40 young men has a thyroid nodule. More than 95% of all thyroid nodules are benign (non-cancerous growths). Some nodules are actually cysts that are filled with fluid rather than thyroid tissue. Most individuals will develop a thyroid nodule by the time they are 50 years old. The incidence of thyroid nodules increases with age; 50% of 50 year olds will have at least one thyroid nodule, 60% of 60 year olds will have at least one thyroid nodule, and 70% of 70 year olds will have at least one thyroid nodule. Individuals do not have to have hypo- and hyperthyroidism to have nodules of the thyroid gland.
Thyroid cancer: Many types of tumors can develop in the thyroid gland. Most of these tumors are benign (non-cancerous). Others are malignant (cancerous), which means they can spread into nearby tissues and to other parts of the body. Anyone can get cancer of the thyroid gland, but certain factors may increase the risk. Risk factors include: being between ages 25-65; being a woman; being Asian; having a family member who has had thyroid disease; or having radiation treatments to the head or neck.
Hyperparathyroidism: The parathyroid glands regulate serum calcium and phosphorus levels through the secretion of parathyroid hormone (PTH), which raises serum calcium levels while lowering the serum phosphorus concentration. The regulation of PTH secretion occurs through a negative feedback loop in which calcium-sensing receptors on the membranes of parathyroid cells trigger decreased PTH production as serum calcium concentrations rise. Primary hyperparathyroidism, which accounts for most presentations of hyperparathyroidism, results from excessive release of PTH and manifests as hypercalcemia. In 80% of patients with hyperparathyroidism, the symptoms of hypercalcemia (high blood levels of calcium) are mild or not notable.
Hypoparathyroidism: Hypoparathyroidism is secretion of too little parathyroid hormone. The symptoms of hypoparathyroidism are the same as hypocalcemia (low blood calcium levels). Symptoms can range from quite mild (tingling in the hands, fingers, and around the mouth) to more severe forms of muscle cramps leading all the way to tetany (severe muscle cramping of the entire body), and rarely convulsions.