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Hyperthyroidism: Glossary

Sunday, April 21, 2013 - 17:42

Contributing Author: Guy Slowik FRCS

Here are definitions of medical terms related to hyperthyroidism.

Adam's apple: Part of the cartilage at the front of the neck that forms the larynx or voice box. It is more prominent visually and by touch in men than in women.

Anti-adrenergic drug: Any of a number of chemical agents that act to suppress the effects of adrenaline. One class is called the beta-blocking drugs.

Anti-thyroid drug: Any one of several chemical agents that interfere and hinder the production of thyroid hormone. Examples are propylthiouracil (PTU), methimazole (Tapazole®), and carbimazole.

Arrhythmia (of the heart): An irregular pulse or abnormal heartbeat.

Atrial fibrillation: Rapid, twitching contractions of one of the upper chambers or atrium of the heart.

Autoimmune disorder: Any one of a number of conditions caused by misdirected activity of the body's own immune system. In people with an autoimmune disorder, the body mistakenly "attacks" its own healthy tissue.

Endocrine gland: A gland that releases a chemical messenger, known as a hormone, directly into the bloodstream that will affect other parts of the body. The thyroid is an endocrine gland.

Endocrinology: The study of the endocrine system and its associated activities. This is a very distinct subspecialty; a physician who practices in this area of medicine is known as an endocrinologist.

Graves' disease: The most common form of hyperthyroidism or high levels of circulating thyroid hormone. Graves' disease is an autoimmune disorder of the thyroid gland that causes excessive production and release of thyroid hormone. Hyperthyroid eye and skin changes are sometimes associated with this condition.

Hashimoto's thyroiditis: An autoimmune disorder of the thyroid gland in which an immune response is misdirected against healthy thyroid hormone.

Homeostasis: A state of balanced function in the body.

Hormone: A chemical substance that is produced by an endocrine gland and released into the bloodstream to have its effect on other parts of the body. Also known as a "chemical messenger". For example, thyroid hormone, released by the thyroid gland speeds up or stimulates certain bodily functions.

Hyperthyroidism: A condition characterized by a high level of circulating thyroid hormone. This may cause the "speeding up" of metabolic activity in body cells.

Hypothyroidism: A condition characterized by a low level of circulating thyroid hormone, causing inadequate stimulation of metabolic activity in body cells.

Immune system: A complex, organized system made up of special proteins, cells, and tissues that function to protect the body against disease-causing organisms such a bacteria or viruses; toxic substances or harmful chemicals; and foreign tissues, such as donor organs, or damaged cells. White blood cells are the primary cells of the immune system.

Immunosuppressive drug: Any of several chemical agents that decrease the function and activities of the immune system. In some cases, this class of drugs suppresses autoimmune activity. An example of an immunosuppressive drug is cyclosporine.

Iodine: A chemical element found in seawater and other sources. This chemical is necessary to produce thyroid hormone. Table salt labeled "iodized" contains added iodine and, for most people, is an important source of dietary iodine.

Metabolism: The chemical and physical processes that create the substances and generate the energy needed for cell function, growth, and division. Metabolism is also known as metabolic activity.

Nodular thyroid disease: A condition of the thyroid gland characterized by areas of overactivity within the thyroid gland. These areas are known as thyroid nodules. The exact cause of nodular thyroid disease, which may result in hyperthyroidism, is not known.

Nucleus: A round or oval structure inside a cell that regulates cellular activities. The nucleus contains genes, the units of heridity, that have a specific location on a chromosome. Genes are duplicated during each cell division. The function of a gene is to direct or "regulate" other proteins, including proteins that control body activities.

Ophthalmology: The study of the eye and its associated parts. This is a specialty in medicine and physicians who devote their practice to eyes and disorders affecting the eyes are called ophthalmologists.

Palpitations: An awareness that the heart is beating irregularly.

Pernicious anemia: A form of anemia or a less than normal level of circulating red blood cells. This condition is caused by an inappropriate autoimmune process that misdirects an immune response against the lining of the stomach. As a result, the stomach lining is damaged and vitamin B12 is not absorbed properly from food that is consumed. Vitamin B12 is necessary for proper red blood cell production.

Pituitary gland: A relatively small endocrine gland about the size of a pea. This gland is located underneath the brain and releases a number of essential hormones, including thyroid stimulating hormone (TSH).

Pretibial myxedema: A skin condition characterized by swollen, itchy patches of skin on the front of the lower legs or shins. This condition is associated with Graves' disease.

Primary hyperthyroidism: A form of hyperthyroidism in which the disease process occurs within the thyroid gland itself. Graves' disease is the most common form of primary hyperthyroid disease, followed by nodular thyroid disease.

Radioactive iodine: Iodine that contains a radioactive component. This element is chemically depicted as 131I. This form of iodine, which puts out intense energy, is used in a special test to diagnose thyroid disease.

Radioactive iodine uptake (RAIU) scanning: A special test used to diagnose thyroid disease. During this procedure, the amount of iodine "taken up" by the thyroid is measured and images or "pictures" of the thyroid gland are taken. So-called hot spots, or areas of particularly strong energy, represent areas of increased hormone production. Cold spots, or particularly weak energy spots, represent poorly functioning or nonfunctioning areas of the thyroid gland.

Retrospective: Literally, a look back in history. A "retrospective study" reviews the treatment of a disease over a period of time and the individual's long-term response to therapy.

Steroids: A class of strong anti-inflammatory drugs that used to treat a variety of diseases, including certain autoimmune disorders.

Subtotal thyroidectomy: A surgical procedure during which part of the thyroid gland is surgically removed through an incision in the front of the neck.

T3: A term used to describe a form of thyroid hormone in the bloodstream. It has three units of iodine attached to the hormone structure. T3 is biologically active.

T4: A term used to describe a form of thyroid hormone in the bloodstream. This form has four iodine units attached to the hormone structure. Most thyroid hormone in the blood is T4; however, it is not biologically active in the body. Special cells convert T4 into T3.

Thyroid gland: A small, butterfly-shaped endocrine organ located in the neck below and in front of the Adam's apple. The thyroid gland weighs about 20 to 25 grams and produces thyroid hormone, which is released into the bloodstream.

Thyroid hormone: A chemical substance produced by the thyroid gland and released into the bloodstream. It interacts with almost all body cells, causing them to increase their metabolic activity. Two forms of thyroid hormone, abbreviated as T3 and T4, are found in bloodstream.

Thyroid-stimulating hormone (TSH): A hormone produced and released into the bloodstream by the pituitary gland, which is located underneath the brain. TSH interacts with thyroid cells, causing them to produce and release thyroid hormone into the blood.

Thyrotoxicosis: Another name for hyperthyroidism or high levels of thyroid hormone. Term comes from prefix "thyro-" meaning thyroid, the root "toxic" meaning harmful, and the suffix "-osis" meaning condition.

Vitamin B12: A chemical substance found almost exclusively in meats. This vitamin is necessary for certain chemical processes in the body, including the ongoing production of red blood cells.