Saying that someone has a goiter is the same thing as saying that they have an abnormally enlarged thyroid gland. This does not necessarily mean that the thyroid gland is not performing properly. For example, it may make too little hormone, too much hormone, or the right amount of hormone. The most common cause of a goiter is when people do not have enough iodine in their diet. In addition, thyroid nodules may cause goiter (multinodular goiter).
A thyroid cyst is different. A thyroid cyst is a thyroid nodule that is filled with fluid, such as blood. Sometimes these cysts have some solid material in them as well and these cysts are called complex cysts. Most of the time they are very small but they can become large enough that they can bee seen on the neck.