Hyperthyroidism is the overproduction of thyroid hormones by an overactive thyroid (Norris, 1999). The thyroid gland is located in the front of the neck, and produces the hormones thyroxine (T4) and triiodothyronine (T3) that regulate the body's metabolic rate by helping to form RNA and increasing oxygen absorption in every cell. Production of these hormones is controlled by thyroid-stimulating hormone (TSH), which is secreted by the pituitary gland.
Hyperthyroidism occurs when thyroid hormone production increases despite the level of TSH. The excessive amount of hormones in the bloodstream increases the body's metabolic rate, and causes both mental and physical symptoms. Other names for hyperthyroidism include Grave's disease, diffuse toxic goiter, Basedow's disease, Parry's disease and thyrotoxicosis.
Hyperthyroidism can be caused by an autoimmune reaction in which the body makes antibodies that cause the thyroid to grow and secrete excess hormone. This is thought to be the cause of Grave's disease (Berkow, Beers and Fletcher, 1997). The condition may be hereditary. In toxic nodular goiter, one or more nodules in the thyroid produce excess thyroid hormone and are not under TSH control. The nodules are benign thyroid tumors, and this form of hyperthyroidism is usually present only in older people.
Symptoms of hyperthyroidism include weight loss with increased appetite, shortness of breath and fatigue, intolerance to heat, heart palpitations, increased frequency of bowel movements, weak muscles, tremors, anxiety and difficulty sleeping (Norris, 1999). Women with hyperthyroidism may develop decreased menstrual flow and irregular menstrual cycles.
Patients with Grave's disease often have goiter - a visible enlargement of the thyroid gland - and may have bulging eyes. A serious form of hyperthyroidism, known as thyroid storm, may show up as sudden and acute symptoms, some of which mimic typical hyperthyroidism, ...