High Thyroid
What is hyperthyroidism?
Hyperthyroidism is a condition in which an overactive thyroid gland is producing an excessive amount of thyroid hormones that circulate in the blood. ("Hyper" means "over" in Greek).
What are thyroid hormones?
Thyroid hormones stimulate the metabolism of cells. They are produced by the thyroid gland. The thyroid gland is located in the lower part of the neck, below the Adam's apple. The gland wraps around the windpipe (trachea) and has a shape that is similar to a butterfly formed by two wings (lobes) and attached by a middle part (isthmus).
The thyroid gland removes iodine from the blood (which comes mostly from a diet of foods such as seafood, bread, and salt) and uses it to produce thyroid hormones. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3) representing 99.9% and 0.1% of thyroid hormones respectively. The hormone with the most biological activity (i.e., the greatest effect on the body) is actually T3. Once released from the thyroid gland into the blood, a large amount of T4 is converted to T3--the more active hormone that affects the metabolism of cells.
Thyroid hormone regulation--the chain of command
The thyroid itself is regulated by another gland located in the brain, called the pituitary. In turn, the pituitary is regulated in part by thyroid hormone that is circulating in the blood (a "feedback" effect of thyroid hormone on the pituitary gland) and in part by another gland called the hypothalamus, also a part of the brain.
The hypothalamus releases a hormone called thyrotropin releasing hormone (TRH), which sends a signal to the pituitary to release thyroid stimulating hormone (TSH). In turn, TSH sends a signal to the thyroid to release thyroid hormones. If overactivity of any of these three glands occurs, an excessive amount of thyroid hormones can be produced, thereby resulting in hyperthyroidism.
The rate of thyroid hormone production is controlled by the pituitary gland. If there is an insufficient amount of thyroid hormone circulating in the body to allow for normal functioning, the release of TSH is increased by the pituitary in an attempt to stimulate the thyroid to produce more thyroid hormone. In contrast, when there is an excessive amount of circulating thyroid hormone, the release of TSH is reduced as the pituitary attempts to decrease the production of thyroid hormone.
What causes hyperthyroidism?
Some common causes of hyperthyroidism include:
- Graves' Disease
- Functioning adenoma ("hot nodule") & Toxic Multinodular Goiter (TMNG)
- Excessive intake of thyroid hormones
- Abnormal secretion of TSH
- Thyroiditis (inflammation of the thyroid gland)
- Excessive iodine intake Graves' Disease
What are the symptoms of hyperthyroidism?
Hyperthyroidism is suggested by several signs and symptoms; however, patients with mild disease usually experience no symptoms. In patients older than 70 years, the typical signs and symptoms also may be absent. In general, the symptoms become more obvious as the degree of hyperthyroidism increases. The symptoms usually are related to an increase in the metabolic rate of the body. Common symptoms include:
- Excessive sweating
- Heat intolerance
- Increased bowel movements
- Tremor (usually fine shaking)
- Nervousness; agitation
- Rapid heart rate
- Weight loss
- Fatigue
- Decreased concentration
- Irregular and scant menstrual flow
In older patients, irregular heart rhythms and heart failure can occur. In its most severe form, untreated hyperthyroidism may result in "thyroid storm," a condition involving high blood pressure, fever, and heart failure. Mental changes, such as confusion and delirium, also may occur.
Source: MedicineNet.com
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