Uric acid is the end product of the normal degradation of substances called purines, which are essential constituents of DNA found in all cells of the body. Uric acid in blood is maintained within a particular range, and deranged levels may cause, or be reflective of, disease. DNA holds the unique genetic code of every living organism. It is normally composed of four nitrogenous bases: adenine, guanine, cytosine and thymine. Adenine and guanine are also known as the purines, while cytosine and thymine are the pyrimidines. Purines are special in that they have a special biochemical pathway dedicated to their degradation and breakdown. Adenine and guanine are sequentially degraded by several enzymes to xanthine and hypoxanthine, which are then oxidized by a final enzyme, called xanthine oxidase, to produce uric acid. The kidneys excrete uric acid in urine.
The normal range for uric acid concentration in blood is generally between 3.0 and 8.0 mg/dL, although there are slight variations depending on the standards used by the testing laboratory. A condition of excessive uric acid in blood is referred to as hyperuricemia, while a condition of deficient levels is known as hypouricemia. Most diseases related to uric acid metabolism are caused by hyperuricemia. Gout is a type of arthritis caused by the accumulation of needlelike crystals of uric acid in the joints. Excess uric acid in urine may crystallize and cause stone formation in the kidneys and the urinary tract. Lesch-Nyhan syndrome, a rare inherited defect of enzymes that salvage purines, is associated with severe hyperuricemia and bizarre episodes of self-mutilation.
Hypouricemia, on the other hand, is a benign finding. Instead of causing disease, low uric acid is a sign that leads doctors to suspect that there is another ongoing disease process or medical condition. Most of the time, hypouricemia is a side effect of medications or a toxicity of certain substances. In other cases, it is due to diet, genetics or an underlying medical condition.
The majority of drugs that cause hypouricemia are those that cause increased urinary excretion of uric acid. Examples of these drugs, also known as uricosurics, are xanthine oxidase inhibitors (such as allopurinol), colchicines, uricase oxidase (such as rasburicase) and phosphate binders (such as sevelamer).
3. Vegetarian Diet
If you are a vegetarian, you are likely to have lower-than-normal uric acid levels. Vegetables generally have lower purine contents compared to meat products.
Inherited conditions that cause hypouricemia are either deficiencies in the enzymes responsible for normal purine metabolism or mutations causing abnormally high kidney excretion of uric acid. The latter mutations, collectively known as familial renal hypouricemia, make the kidney inefficient in reabsorbing uric acid that is filtered from the blood.
5. Medical Conditions
Medical conditions that present with low blood uric acid are very diverse, and, more often than not, there are no clear-cut patterns that identify these conditions. In cases of hypouricemia, it is helpful to get in touch with a physician to rule out diseases such as Fanconi syndrome, hyperthyroidism, multiple sclerosis, multiple myeloma, nephritis and Wilson's disease.