The thyroid is a butterfly-shaped gland in the front of the neck. It produces hormones that control the speed of your metabolism -- the system that helps the body use energy. Thyroid disorders can slow down or rev up metabolism by disrupting the production of thyroid hormones. When hormone levels become too low or too high, you may experience a wide range of symptoms. An unexplained change in weight is one of the most common signs of a thyroid disorder. Weight gain may signal low levels of thyroid hormones, a condition called hypothyroidism. In contrast, if the thyroid produces more hormones than the body needs, you may lose weight unexpectedly. This is known as hyperthyroidism. Hypothyroidism is far more common. A swelling or enlargement in the neck is a visible clue that something may be wrong with the thyroid
