Goitre is seen in both hyper and hypothyroidism. Comment.

The term goiter refer to the abnormal enlargement of thyroid gland. It is important to know that presence of goiter does not mean that the gland is malfunctioning. One of the most common cause of goiter formation worldwide is iodine deficiency. The primary activity of thyroid gland is to concentrate iodine from blood to make thyroid hormone. The gland cannot make enough thyroid hormone if it does not have enough iodine i.e., with iodine deficiency the individual will become hypothyroid. Consequently, the pituitary gland in brain senses the thyroid hormone level is too low and sends signal to thyroid. This signal is called thyroid stimulating hormone. This hormone stimulates the thyroid to produce thyroid hormone and to grow in size. This abnormal growth in size produces goiter. Thus iodine deficiency is one cause of goiter development. Another common cause of goiter is Grave's disease. In this one immune system produces a protein called thyroid stimulating immunoglobulin (TSI). As with TSH, TSI stimulate the thyroid gland to enlarge produce a goiter. However, TSI also stimulates the thyroid to make too much thyroid hormone (causes hyperthyroidism). Since pituitary senses too much thyroid hormone, it stop secreting TSH. Inspite, thyroid gland continues to grow and make thyroid hormone.