Metabolism is the term to describe the myriad of chemical reactions that the body's cells carry out to generate energy. The main hormone that increases metabolism in the body is the thyroid hormone. This hormone, secreted by the thyroid gland, affects all tissues in the body to increase the metabolic rate, increasing energy production. Conditions affecting the secretion of thyroid hormone can also affect the body's metabolic rate.
Thyroid Gland and Hormones
The thyroid is a butterfly shaped gland located in the neck, below the larynx or voice box. In response to the brain's secretion of thyroid-stimulating hormone, the thyroid gland releases the hormones that affect the body's metabolism. The thyroid needs iodine ingested in the diet to produce thyroid hormones. An abnormal increase in the secretion of thyroid hormone is called hyperthyroidism; hypothyroidism refers to an abnormal decrease in the body's thyroid hormone level. Conditions that cause hyperthyroidism cause an increase in the baseline metabolic rate.
Causes
There are many causes for an overactive thyroid. According to Medline Plus, these include taking too much iodine in the diet; a condition called Graves' disease, an autoimmune condition that causes overstimulation of the thyroid; thyroiditis, or inflammation of the thyroid; and tumors of the thyroid or the pituitary. Other causes include taking too much prescription thyroid hormone and supplements like coconut oil, kelp and green tea that can stimulate the thyroid.
Symptoms
Because the thyroid affects the body's metabolism, excess thyroid hormone results in symptoms related to the increase in the metabolic rate. According to MayoClinic.com, symptoms of hyperthyroidism include weight loss despite an increase in appetite, restlessness, tachycardia or rapid heart rate, and nervousness and irritability. Sweating and sensitivity to heat can also result and reflect the increased energy production. Other symptoms include enlargement of the thyroid, or a goiter; protruding eyeballs; fatigue and difficulty sleeping.
Hyperthyroidism treatment
The treatment of hyperthyroidism aims to slow down the metabolic rate by either blocking the effects of thyroid hormone, or decreasing its secretion. The treatment also depends on the cause of hyperthyroidism. In general, medicines include radioactive iodine, which destroys part or the entire thyroid; anti-thyroid medications, like propylthiouracil, that decrease the secretion of thyroid hormone; beta blockers, that reduces the effect of excess thyroid hormone on the heart; and surgery to remove part or the entire gland.
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