The thyroid is a butterfly-shaped gland located just below Adam's apple on the neck. In response to signals from the brain, it secretes thyroid hormones, which are involved in the body's metabolism -- the speed at which the body executes its various functions -- temperature control and heat production. The body tightly controls the level of thyroid hormone, since low and high thyroid levels can produce a variety of symptoms and have serious health consequences.
The Facts
The pituitary is a walnut-shaped gland that sits below the brain and controls the thyroid by secreting a hormone called TSH. This hormone travels through the blood stream to the thyroid and either stimulates its production of thyroid hormone or to turn down its secretion. High or low thyroid levels can result from a number of conditions. Iodine is an integral element in the production of thyroid hormone.
High Thyroid Levels
According to the Merck Manuals, the most common cause of hyperthyroidism, or high thyroid levels, is Graves' disease. This is an autoimmune disorder, in which the body makes a protein that stimulates the thyroids to produce too much thyroid hormone. Other causes of high thyroid levels include thyroiditis, or inflammation of the thyroid, which include Hashimoto's thyroiditis, a condition in which the inflammation causes the release of stored thyroid hormones.
Symptoms of Hyperthyroidism
The symptoms of hyperthyroidism include rapid heart rate and palpitations, or skipped heart beats; excessive sweating; hand tremors or shakiness; difficulty sleeping or concentrating; anxiety; diarrhea and weight loss. The thyroid gland can also become so inflamed as to cause a goiter, which can be painful. Another symptoms of hyperthyroidism is exophthalmos, or a distinctive bulging of the eyes, and double vision.
Low Thyroid Levels
According to the Mayo Clinic, one of the most common causes of hypothyroidism, or low thyroid hormone levels, is Hashimoto's thyroiditis. Initially, Hashimoto's causes increased thyroid hormone release. As the disease progresses it causes destruction of the thyroid tissue, resulting in hypothyroidism. Another common cause of hypothyroidism is treatment of hyperthyroidism. One of these treatments results in destruction of the thyroid tissue, which the makes the patient hypothyroid.
Symptoms of Hypothyroidism
The most common symptoms of hypothyroidism include weight gain, fatigue, sluggishness, constipation, extreme sensitivity to cold temperatures, and constipation. Other symptoms include facial puffiness, a hoarse voice, abnormally heavy menstrual periods in women, brittle fingernails and hair, and depression.
