As the body uses up protein, ammonia
is produced as one of the waste by-products. Ammonia
is toxic to the body, so it is processed by the liver into the less toxic substance urea. If the liver is diseased (e.g. liver cancer), it's capacity to detoxify ammonia may be greatly reduced, leading to increased circulating levels of this harmful substance. Increased blood levels of ammonia therefore indicate a worsening of the liver cancer, and possibly liver failure.