Tip - How does the thyroid work? - PubMed Health - National Library of Medicine - PubMed Health

The thyroid is a vitally important hormonal gland that regulates metabolism and growth in the body. The thyroid hormones T3 and T4 increase the basal metabolic rate. In other words, they make the body cells work harder, using more energy. If more energy is needed for metabolic processes in the body – for instance for growth, when it is cold, or during pregnancy – more hormones are produced and transported into the blood.
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