Asymmetrical goitre. Scintigram of the enlarged left lobe (goitre, right) of a thyroid gland. The thyroid is an endocrine gland found in the neck, responsible for the production of hormones controlling the body's metabolism. Goitres most commonly occur as a result of a lack of dietary iodine, which affects the synthesis of the thyroid hormones. Other causes include Graves' disease and thyroid inflammation. Symptoms include weight loss and tremors. A large goitre will cause a person's neck to swell. Treatment may involve iodine replacement or surgical removal. Using the radioactive tracer iodine-123, a scintigram shows the activity of the thyroid gland.