Uric acid, a waste product formed when the body breaks down purines, dissolves in blood and travels to kidneys for excretion. Low uric acid levels, known as hypouricemia, are below 2 milligrams per deciliter (mg/dL).
Kidney-Related Factors
Kidneys regulate uric acid; impaired function can lead to low levels. Renal hypouricemia is a genetic condition where kidneys excrete excessive uric acid.
Gene mutations cause renal hypouricemia. These impair uric acid reabsorption, increasing excretion. They also disrupt uric acid transport, leading to excessive loss.
Fanconi syndrome, a rare kidney disorder, is another cause. Tubules fail to reabsorb substances, causing excessive excretion and lower blood concentrations. These substances include:
- Glucose
- Amino acids
- Phosphates
- Uric acid
Kidney injury or acquired conditions can also lower uric acid.
Systemic Medical Conditions
Systemic conditions can lower uric acid. Severe liver disease reduces uric acid production. As the liver metabolizes purines, impaired function decreases production.
Cancers associate with hypouricemia. Hodgkin’s lymphoma, multiple myeloma, and some solid tumors link to decreased uric acid. Increased renal clearance or reduced production causes this. Mechanisms vary by cancer type and effects.
SIADH can lower uric acid. It leads to excessive antidiuretic hormone release, increasing water retention. Wilson’s disease, characterized by excessive copper accumulation, also contributes to hypouricemia. Copper deposition in kidneys causes renal tubular dysfunction, increasing uric acid excretion.
Medications and Other Influences
Medications contribute to lower uric acid. Uricosuric medications increase kidney uric acid excretion by interfering with reabsorption, promoting elimination and reducing levels. Examples include:
- Probenecid
- High-dose aspirin
- Fenofibrate
- Losartan
Xanthine oxidase inhibitors (e.g., allopurinol, febuxostat) are uric acid-lowering drugs. They reduce uric acid production. They block xanthine oxidase, which forms uric acid. Often used for high uric acid, they can lower concentrations below normal.
Radiographic contrast agents can transiently decrease uric acid after administration. Dietary factors play a role. Extremely low-purine diets limit uric acid precursors, leading to low levels. Excessive fluid intake can dilute blood, reducing uric acid, similar to SIADH.
Implications and When to Consult a Doctor
Low uric acid is often asymptomatic. Some cases carry an increased risk of kidney stones due to excessive uric acid excretion.
Determining the cause of low uric acid is important; management depends on the root issue. Management addresses the underlying condition or adjusts medications. Individuals with concerns should seek medical advice.