Updated September 03, 2013.

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Definition: band of tissue that connects two larger structures. In medicine, the isthmus commonly refers to tissue that forms a bridge between the two lobes of the thyroid, but can reference other points in the body. Examples include isthmus of the Eustachian tubes and isthmus of the uterus.

In relation to thyroid cancer, the isthmus may be removed during a thyroidectomy to treat the disease. The removal of the isthmus is called a isthmusectomy.

Pronunciation: isth-mus