What Is Hyperuricemia?

Blood being drawn for blood test.
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Uric acid, a normal waste product, is the end result of purine metabolism. Purines are naturally-occurring chemicals which are found in our bodies and in our diet. Normally, uric acid dissolves in the blood, is processed through the kidneys, and is eliminated from the body in the urine. A condition, known as hyperuricemia (high uric acid levels in the blood), can occur if there is decreased excretion of uric acid or from increased production of uric acid.

Hyperuricemia may also result from a combination of under-excretion and overproduction. Under-excretion accounts for the majority of cases of hyperuricemia. Overproduction accounts for a relatively small number of hyperuricemia cases. The prevalence of asymptomatic (without symptoms) hyperuricemia in the general population is estimated to be between 2% and 13%.

Approximately two-thirds of total body urate (uric acid) is produced endogenously (within the body), while the remaining one-third is accounted for by the metabolism of dietary purines. Approximately 70% of the urate produced daily is excreted by the kidneys, with the remainder eliminated by the intestines.

Uric Acid Blood Test

The normal range for a uric acid blood test is between 3.5 and 7.2 mg/dL. You should be aware that different laboratories may have slightly different normal reference ranges. Hyperuricemia, specifically, is defined as a uric acid blood level greater than 7mg/dL for men and greater than 6mg/dL for women.

Uric Acid Crystal Formation

While hyperuricemia itself is not a disease, and in some cases causes no problems, a prolonged state of hyperuricemia may lead to the development of crystals. It is the uric acid crystals that are associated with gout. But, even with knowing that, the association between hyperuricemia and gout is not completely clear.

Many patients with hyperuricemia do not develop gout -- and some patients with recurring gout attacks have normal or low blood uric acid levels. Only a small percentage of people with hyperuricemia actually go on to develop gout.

Uric acid crystals, when deposited in the joints, can cause joint pain, joint swelling, joint stiffness, joint deformity, and limited range of motion. If gout does develop, the American College of Rheumatology guidelines on the management of gout (2012) recommend that uric acid levels be maintained at a level below 6 mg/dL to prevent recurring gout attacks.

Uric acid crystals can also be deposited in the kidneys. Uric acid crystals in the kidneys may cause kidney stones to form and potentially lead to kidney disease or kidney failure.

Risk Factors Associated With Hyperuricemia

Hyperuricemia is associated with risk factors, such as dysglycemia (blood sugar disorders), dyslipidemia (lipid disorders), obesity, and abnormal blood pressure -- together known as metabolic syndrome.

Hyperuricemia can be caused by an unhealthy lifestyle, in particular, a poor diet that is high in purines, protein, alcohol, and carbohydrates.

While it is important to pay attention to modifiable risk factors, such as diet and lifestyle, that alone is often insufficient to control hyperuricemia. It is also noteworthy that certain medications may increase the risk of hyperuricemia, including thiazides, loop diuretics, and low dose aspirin.

The Bottom Line

A prolonged state of hyperuricemia, or chronic hyperuricemia, is associated with a greater risk of developing gout. Crystal deposition is the consequence of hyperuricemia that can lead to gout or kidney disease. Maintaining a blood uric acid level below 6 mg/dL is essential for people diagnosed with gout to prevent recurring attacks.

Sources:

Uric Acid - Blood. MedlinePlus. 4/29/2013.
https://www.nlm.nih.gov/medlineplus/ency/article/003476.htm

Chronic Hyperuricemia, Uric Acid Deposit and Cardiovascular Risk. Grassi D. et al. Current Pharmaceutical Design. April 2013.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3606968/

Gout and Hyperuricemia. National Kidney Foundation. Accessed 10/23/2015.
https://www.kidney.org/atoz/content/gout

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