A goitre (sometimes spelt "goiter") is a swelling of the thyroid gland that causes a lump to form in the front of the neck. The lump will move up and down when you swallow. The thyroid gland is a small butterfly-shaped gland in the neck, just in front of the windpipe (trachea). It produces thyroid hormones, which help regulate the body's metabolism, the chemical processes that occur in the body.