Goitre. Swollen neck of a patient with goitre. This is an enlargement of the thyroid gland, usually due to a deficiency of iodine. The thyroid uses iodine to produce hormones that regulate the metabolism. In the absence of sufficient dietary iodine, thyroid stimulating hormone (TSH) is released by the pituitary gland in the brain. This is meant to speed up hormone production, but it also leads to enlargement of the gland. This may cause difficulty breathing or swallowing. The condition is best treated with iodine supplements, but the gland can be removed surgically if it is causing severe problems. An enlarged thyroid may also be due to thyroiditis (an autoimmune disease) or cancer.