Why does TSH need to be suppressed?

When TSH binds to receptors, it also stimulates growth of the cells that form the tissue of the thyroid gland. This may contribute to generalized growth of thyroid tissue with enlargement that forms a goiter. It may also contribute to the growth of isolated regions of tissue that enlarge to form distinct nodules. With this form of therapy, the expectation is that suppression of TSH to lower than normal levels will help to reduce the amount that is available to bind to receptors. This in turn may help to limit further growth of thyroid tissue.

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