A goiter is often noticeable on a person’s neck—it is an enlargement of the thyroid gland caused by hypothyroidism (too little thyroxin hormone in the person’s system). An insufficient dietary intake of iodine is a common cause of goiter, although it may be caused by a cold nodule or tumor on the thyroid, leading to an insufficient amount of thyroxin to enter the system. Goiters are more often treated by supplementation of the thyroid hormone.