What Is Urea?

Urea is an organic compound formed when nitrogen and protein break down and is the main component of human urine. It has many uses, including in fertilizer and other industrial processes and in creams that treat skin disorders, such as psoriasis, eczema, atopic dermatitis, and ingrown nails.

Some individuals have urea cycle disorders that inhibit them from properly disposing of waste, which can lead to neurological symptoms.

Learn more about how the body produces urea, why it is important, its various uses, and the disorders that disrupt its production.

How Is Urea Produced?

Urea is produced through the urea cycle, a biochemical process that the body uses to eliminate waste. Proteins must be broken down regularly from excess protein in the diet or old cells that need replacing. The breakdown of protein creates a toxic substance called ammonia, which humans cannot safely excrete (eliminate).

Instead, we convert ammonia into less toxic urea through a multistep process involving several different proteins. This process occurs in the liver; then, urea is released into the bloodstream, where it travels to the kidneys and is finally excreted as urine.

Urea Cycle Disorders

Sometimes, one or more defects can occur in the proteins involved in the urea cycle, resulting in a urea cycle disorder. When this happens, the body cannot properly process the toxic ammonia waste produced from protein breakdown.

Causes

Urea cycle disorders are typically diagnosed in infancy or childhood and result from a genetic defect inherited from one or both parents. An individual with a urea cycle disorder may have defects in one of the six enzymes or two transport proteins involved in the urea cycle.

Symptoms

The buildup of ammonia in the body can lead to mild-to-severe symptoms, depending on which enzymes are impacted. The symptoms of urea cycle disorders most often affect the brain and nervous system and may be apparent in infancy or early childhood depending on the severity of the defects. Symptoms that may arise in early infancy include:

• Sleepiness or lethargy
• Vomiting or refusal to eat
• Low body temperature (hypothermia)
• Seizures
• Muscle rigidity (posturing)
• Coma
• Respiratory failure

In less severe cases, ammonia levels do not rise as quickly, and symptoms may not be apparent until several months or years after birth. In these cases, symptoms may include:

• Behavioral or psychiatric issues
• Seizures
• Avoidance of protein foods
• Nausea and vomiting

Diagnosis

Urea cycle disorders are diagnosed by a healthcare provider, who will review your or your child's symptoms and medical history. One of the hallmark signs of a urea cycle disorder is hyperammonemia (high ammonia levels).

Other blood tests and genetic tests will confirm a suspected urea cycle disorder if hyperammonemia is identified. Some congenital (found-at-birth) defects associated with a urea cycle disorder are tested during routine newborn screening, though not all.

Treatment

When diagnosed, the high ammonia levels must be removed from the body using dialysis (a blood-filtering procedure). Further treatment depends on the severity of the disorder, age, coexisting medical conditions, and other factors.

Nutrition support and dietary modifications are usually necessary to manage urea cycle disorders long term. Your healthcare provider will likely recommend a low-protein diet to decrease the metabolic waste produced in the body and vitamin and mineral supplements to ensure nutritional adequacy. 

For some, a liver transplant may be an option to cure a urea cycle disorder completely. This will not reverse any existing neurological damage caused by hyperammonemia but can help an individual lead a more normal healthy life.

Urea Uses

Outside the human body, urea has several uses. It is used in agriculture as a fertilizer due to its high nitrogen content. It also has uses in other industries and can be found in animal feed, barbituric acid, cold packs, and other products.

Urea is also widely used in dermatology as a topical cream for treating skin conditions such as eczema, psoriasis, atopic dermatitis, ichthyosis, xerosis, seborrheic dermatitis, and others. This is in part because urea is what’s known as a hygroscopic molecule, meaning it is capable of absorbing water.

Urea also has antimicrobial properties and improves skin barrier function. It is one of the most common moisturizing agents and has few mild side effects, making it a safe option for treating many skin conditions that result in scaly, dry skin.

Summary

Urea is an organic compound that is the main component of urine. It is produced from the breakdown of proteins into ammonia to create a less toxic substance that the body can eliminate.

Specific genetic defects can cause urea cycle disorders, causing a buildup of ammonia that can lead to severe symptoms, such as neurological damage. Urea has other uses outside the body, such as in nitrogen-rich fertilizer in agriculture and moisturizing topical cream in dermatology. 

A Word From Verywell

It can be challenging to receive a urea cycle disorder diagnosis for yourself or your child. But know that one can live a long, happy life with proper disease management.