The thyroid gland is a butterfly-shaped gland located in the front of the neck. The thyroid gland produces two hormones, triiodothyronine, or T3, and thyroxine, or T4, that help control metabolism, breathing, heart function, nervous system functioning, body temperature, cholesterol levels and weight, according to the National Endocrine and Metabolic Diseases Information Service. When the thyroid gland produces an excess amount of these hormones, it can result in weight loss.
Control of the Thyroid
The hypothalamus, which is located at the base of the brain, controls another gland called the pituitary gland. When stimulated by the hypothalamus, the pituitary gland releases a hormone called the thyroid-stimulating hormone, or TSH. TSH then stimulates the thyroid gland to release the two thyroid hormones. Any disruption in this process can trigger the thyroid gland to release an excess amount of thyroxine. Excess thyroxine can increase the breakdown of fats and carbohydrates as well as increase the rate of metabolism. The combination of nutrient breakdown and increased metabolism leads to increased weight loss, even with normal food consumption. The overproduction of thyroxine by the thyroid gland is a condition referred to as hyperthyroidism.
Causes of Hyperthyroidism
A common cause of hyperthyroidism is a condition called Graves' disease, which is an autoimmune disorder in which antibodies in the immune system signal the thyroid gland to produce excess amounts of thyroxine. Other causes of hyperthyroidism include inflammation of the thyroid gland and growths on the thyroid that signal hormone production.
Symptoms
Weight loss is a common symptom of hyperthyroidism, but because the thyroid hormones control so many body processes, there are a variety of other symptoms as well. Symptoms of hyperthyroidism include nervousness, irritability, fatigue, difficulty sleeping, intolerance to heat, irregular heartbeat, increase in heart rate, hand tremors, diarrhea and mood swings, according to the National Endocrine and Metabolic Diseases Information Service. Those with hyperthyroidism may also develop goiter, which is a physically enlarged thyroid gland that gives the neck a swollen appearance.
Treatment
According to the Mayo Clinic, the best treatment option for hyperthyroidism depends on age, physical condition and severity of the hyperthyroidism. A common treatment for hyperthyroidism is a medication called radioactive iodine, which is taken orally. Radioactive iodine is absorbed by the thyroid gland and causes it to shrink. Other treatment may include beta blockers and anti-thyroid medications. Severe cases of hyperthyroidism may require the surgical removal of the thyroid gland.
Complications
Treatment for hyperthyroidism may lead to the opposite condition, hypothyroidism, which is characterized by an underproduction of thyroid hormones. If hypothyroidism develops, it may be necessary to take synthetic thyroid hormones regularly.
