The thyroid gland is located on the front of the neck on the trachea ("windpipe") underneath the skin and muscle layers. It is described as butterfly shaped with "wings" formed by the right and left lobes which wrap around the trachea. The sole function of the thyroid gland is to produce thyroid hormones which regulate the body's metabolism. Metabolism is the conversion of oxygen and calories into energy. The metabolism of every cell in the body is regulated by thyroid hormones. The thyroid gland is controlled by another small gland at the base of the brain called the pituitary gland. When levels of thyroid hormones drop below normal, the pituitary releases thyroid stimulating hormone (TSH) which stimulates the thyroid to release more hormones. The pituitary gland is controlled by another gland in the brain called the hypothalamus. The hypothalamus releases thyroid releasing hormone (TRH) which stimulates the release of TSH.

The thyroid gland is prone to several problems. The problems include the production of too much (hyperthyroidism) or too little (hypothyroidism) thyroid hormone, enlargement of the thyroid gland, the formation of lumps or nodules on the thyroid gland, and thyroid cancer.

Thyroiditis is an inflammation of the thyroid gland. The most common form is known as Hashimoto's disease. In this syndrome the inflammation causes the thyroid gland to become less efficient at converting iodine into thyroid hormone, which causes the gland to enlarge. The lack of thyroid hormone causes the pituitary to release more TSH but the thyroid cannot make more hormone, resulting in hypothyroidism. The treatment is to give thyroid hormone replacement which corrects the hypothyroidism and reduces the enlargement of the thyroid. Thyroid antibodies are present in 95% of cases and are useful in the diagnosis of the disease.

Hypothyroidism occurs when there is insufficient thyroid hormone to regulate the body's metabolism. Symptoms of hypothyroidism are associated with slow metabolism and include fatigue, weakness, weight gain, dry hair and skin, hair loss, intolerance of cold, muscle cramps, constipation, depression, irritability, memory loss, abnormal menstrual cycles, and decreased libido. Thyroid hormone replacement is the usual treatment.

Hyperthyroidism occurs when too much thyroid hormone is produced. Common symptoms of hyperthyroidism include heart palpitations, intolerance of heat, nervousness, insomnia, weight loss, and warm moist skin. Hyperthyroidism can be treated with medications that reduce the production of thyroid hormones. A major drawback is that the condition returns when the medication is discontinued. Other treatment options involve "killing" the thyroid gland with the use of radioactive iodine or surgical removal of the thyroid gland. Thyroid hormone replacement is required after treatment to maintain normal hormone levels.

Reference: http://www.endocrineweb.com/thyroid.html.

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