About Urea Cycle Disorders

The Urea Cycle plays an important role in how humans process protein and remove ammonia from the blood stream. When protein is eaten, the body breaks it down into amino acids, which are used to help the body grow and repair tissue. Any parts of the amino acids not used are turned into a waste product called ammonia (mostly nitrogen).

Ammonia is removed in the Urea Cycle, where enzymes in the liver turn the ammonia into urea, which then leaves the body in the urine. The urea cycle is controlled by six enzymes in the liver. Babies and older patients with UCD are either missing, or do not make enough of, one of these six enzymes. This means they cannot process waste from protein correctly, and ammonia builds up in the blood stream. Ammonia is highly toxic and can cause very serious problems, such as coma or even death.

The Urea Cycle

There are therapies for patients with a Urea Cycle Disorder, but there is no cure for Urea Cycle Disorders. These therapies, or treatments, reduce high ammonia concentrations in the blood in combination with a low protein diet, but they do not always work, and babies can still suffer from high ammonia levels in the blood. Liver transplantation can also be used as a treatment but cannot be performed in newborns.