urates

Urates are salts and esters derived from uric acid. In the body, the urate ion is the predominant form of uric acid at physiological pH. Common urate salts include sodium urate and potassium urate. Urate crystals, such as monosodium urate, can form when concentrations exceed solubility, particularly in cooler or less well-ventilated tissues, and can deposit in joints and soft tissues.

Uric acid is the end product of purine metabolism in humans because the enzyme uricase, which further degrades uric acid in many other organisms, is absent. Uric acid is produced mainly in the liver and is excreted by the kidneys, with a smaller amount eliminated in the gut. Serum urate levels reflect the balance between production and excretion and are influenced by diet, kidney function, medications, and hormonal factors. In the kidney, urate is filtered, secreted, and reabsorbed by several transporters, including URAT1 and GLUT9, contributing to its regulation.

Clinically, elevated urate levels (hyperuricemia) can lead to gout, a disease characterized by deposition of monosodium urate crystals in joints, provoking inflammatory arthritis. Hyperuricemia can also cause urate nephrolithiasis (kidney stones) and, in some cases, urate nephropathy. Diagnosis relies on serum urate measurement and identification of urate crystals in joint aspiration (often showing negative birefringence under polarized light). Management includes urate-lowering therapies such as allopurinol or febuxostat, and uricosurics in some cases, alongside treatment of acute flares with anti-inflammatory medications. Lifestyle measures, including reduced intake of purine-rich foods and alcohol, adequate hydration, and weight management, support long-term control.