What is the function of the thyroid gland?

The thyroid gland is an endocrine gland, which secretes a hormone to control the metabolic rate of the body. This is the rate at which the body burns energy to maintain the normal functions of life and the rate of growth or replacement of body tissue.

Thyroid hormone controls the rate at which oxygen is used in the tissues and also the production of protein within the body. The metabolic rate varies depending on the demands made on the body at any given time from a baseline level at rest, increasing as the person exercises or in response to other factors such as illness or infection.

Changes in metabolic rate are reflected by changes in pulse rate, cardiac output, respiratory rate and heat production. Abnormal increase in production of thyroid hormone is known as thyrotoxicosis or hyperthyroidism and reduced thyroid function is known as myxoedema or hypothyroidism.