The Endocrine System and Hyperthyroidism

The endocrine system is a group of organs and tissues that are responsible for releasing hormones into the bloodstream that regulate growth, development, metabolism, and the function of many tissues. Some of the most prominent parts of the endocrine system are the pituitary gland, the adrenal glands, the thyroid gland and the parathyroid gland, the pancreas, and the ovaries and testes. The pituitary gland is located at the base of the brain and controls many other glands in the body. It also releases endorphins, which are natural pain killers. The adrenal glands are found on top of the kidneys and produce adrenaline and norepinephrine, which help us cope in emergencies. The outer part of the adrenal glands secretes cortisone and hydrocortisone which help people deal with stress and the "maintenance of life." The thyroid gland is a butterfly shaped gland in the neck. This gland stimulates metabolism and increases oxygen consumption, which "regulate the growth and maturation of body tissues and affect physical and mental alertness." The pancreas produces insulin (affects metabolism) and glucagon (raises blood sugar levels). It also releases digestive juices into the upper small intestine. The ovaries and testes, two reproductive organs, release estrogen and testosterone, respectively. The ovaries produce the eggs, and the testes produce sperm. Another hormone produced by the ovaries is progesterone, which regulates the uterine lining and maintains pregnancy.

The thyroid gland affects how many calories people burn, the body temperature, and weight. The thyroid hormones also make the heart beat faster and harder. In effect, all cells increase their activity in the presence of thyroid hormones. Hyperthyroidism is a condition in which the thyroid gland over produces its hormones. Common symptoms are heart palpitations, breathlessness, fatigue, heat intolerance, nervousness, increased bowel movements, insomnia, and light or absent menstrual periods. Less common but more severe symptoms are a faster heart rate, weight loss, hair loss, trembling hands, a tendency to stare, muscle weakness, and warm, moist hands. These symptoms are usually very gradual in appearing so that many patients fail to realize they even have symptoms until they become more severe. In older patients with hyperthyroidism, many of the symptoms can be absent, with only weight loss and depression apparent.

Several causes of hyperthyroidism are known today. Usually the entire gland is overproducing the hormone, although sometimes it's just a single nodule that is responsible. The most common cause of hyperthyroidism is an autoimmune disorder called Graves' disease. This condition is marked by an enlarged thyroid that produces an excessive amount of the thyroid hormone. Graves' disease is called an autoimmune disease because the immune system attacks the thyroid gland. Hyperthyroidism is only one part of Graves' disease; the other two parts of the disease are a swelling of the tissues around the eyes and a thickening of the skin over the lower legs. Usually the eye inflammation resolves gradually once the hyperthyroidism is controlled.

Toxic nodular goiter, or small benign nodules in the thyroid gland that overproduce thyroid hormones, is another cause of hyperthyroidism. In this condition, nodules within the thyroid gland lose their regulatory control, which dictates how much hormone should be produced. Without this controlling mechanism, the cells in the affected area release thyroid hormones at an excessive rate, causing hyperthyroidism.

When the thyroid becomes inflamed (a condition known as thyroiditis), the release of thyroid hormone stored in the gland can increase. In a painful form of thyroiditis, the inflammation is caused by a virus and the symptoms of hyperthyroidism will disappear after a few weeks. One of the more common forms of thyroiditis, called postpartum thyroiditis, occurs in about 5% of women who have just given birth. Despite the fact that symptoms of hyperthyroidism caused by thyroiditis are the same as symptoms caused by other diseases, thyroiditis usually only lasts a few weeks until the store of thyroid hormone is expended.