Urates are salts that originate from uric acid, a natural waste product formed in the body. Uric acid is the end result of the body processing compounds called purines. If the body struggles to properly manage uric acid, these urates can accumulate in various tissues or solidify into crystals within the joints.
Formation of Urates
Purines are organic compounds found naturally within every cell of the human body, serving as building blocks for genetic material like DNA and RNA. Beyond internal production, purines are also present in various foods and beverages that people consume. Approximately two-thirds of the body’s uric acid comes from internally produced purines, while the remaining one-third comes from dietary sources.
The process of purine breakdown, known as purine metabolism, leads to the formation of uric acid. During this process, purines like adenine and guanine are converted into intermediate compounds. For example, adenine can be oxidized to hypoxanthine, which then transforms into xanthine. Guanine also converts to xanthine.
Xanthine oxidase, an enzyme primarily located in the liver, plays a significant role in this final step, converting both hypoxanthine and xanthine into uric acid. Foods particularly rich in purines include:
Red meat
Organ meats (such as liver)
Certain seafood (like anchovies, sardines, mussels, scallops, trout, and tuna)
Alcoholic beverages, especially beer, and drinks sweetened with fructose, a type of sugar, can also contribute to higher uric acid levels.
Body’s Processing and Elimination of Urates
The body handles and removes uric acid to maintain a healthy balance. Under normal circumstances, uric acid dissolves in the blood, allowing it to be transported throughout the body. From the bloodstream, the kidneys are primarily responsible for filtering out this uric acid.
Once filtered by the glomeruli in the kidneys, the uric acid then moves into the renal tubules. Here, reabsorption and secretion occurs, mainly in the proximal tubules. Most of the filtered uric acid is reabsorbed back into the bloodstream, while a smaller portion is ultimately excreted in the urine.
Specialized transporter proteins in the kidney tubules facilitate the reabsorption of urate. Most daily uric acid is eliminated through the kidneys, with the remainder excreted via the gastrointestinal tract. This balanced system ensures that uric acid levels in the body remain within a healthy range.
Health Implications of Urate Imbalance
When the body produces too much uric acid or struggles to excrete it efficiently, levels in the blood can rise, a condition known as hyperuricemia. This imbalance can lead to the formation of sharp, needle-like urate crystals. These crystals can accumulate in various parts of the body, particularly in and around joints, leading to inflammation and pain.
One common condition resulting from urate crystal accumulation is gout, a type of inflammatory arthritis. Gout attacks often manifest as sudden, severe pain, swelling, redness, and tenderness in one or more joints, frequently affecting the big toe. The pain can be intense, peaking within 4 to 12 hours of onset, and lingering discomfort may persist for days to weeks even after the most severe pain subsides. If left untreated, chronic high uric acid levels can lead to the formation of hard, painless deposits of urate crystals under the skin, called tophi, which can develop in areas like:
Fingers
Hands
Feet
Elbows
Achilles tendons
Urate crystals can also form in the kidneys, leading to the development of kidney stones. These stones are solid masses of minerals and salts that can cause pain as they irritate or block parts of the urinary system. Symptoms of uric acid kidney stones may include:
Pain in the lower back, sides, or groin
Increased urge to urinate
Pain during urination
Difficulty urinating
Blood in the urine
Foul-smelling urine
While small stones might pass on their own, larger ones can block the urinary tract, leading to significant discomfort and potentially requiring medical intervention.