Uric acid

White odourless and tasteless powder. Uric acid is almost insoluble in water, ethanol and ether. The substance is easily soluble in alkaline solutions. The salts of uric acid are called urates.
Uric acid occurs naturally as an end product of animal protein metabolism in the excrements of birds and reptiles (it is obtained in large quantities from guano). Little is excreted in the urine of mammals. In humans, as a final product of the purine metabolism, about 0.5-1.0g is excreted daily, the largest part (80%) through the urine.

Increased uric acid concentrations (hyperuricemia) in the blood often indicate kidney dysfunction or a genetic (primary gout) degradation disorder.
The intake of purine-rich meals (meat, offal, possibly in combination with alcohol) increases the uric acid level in the serum. Likewise the values increase, with an increased cell turnover, e.g. in the context of a chemotherapy. In affluent countries, about 20% of men have hyperuricemia (>6.4mg/dl), and manifest gout is found in 1-2% of the population. In women, uric acid usually increases only after menopause (estrogens have a uricosuric effect).
In the case of kidney dysfunction, uric acid is also no longer excreted adequately. This also leads to an increase in the uric acid concentration in the blood (see gout M10.99).
Primary gout (most frequently >99% of cases), which is due to multifactorially inherited defects in uric acid metabolism, is predominantly caused by a renal tubular excretion disorder; only 1-2% are due to endogenous overproduction (e.g. in the X-linked Lesch-Nyhan syndrome ).
If the uric acid concentration exceeds critical values (exceeding the solubility product for Na-urates), uric acid crystals form which are deposited in the joints and trigger inflammatory reactions (gout attack).The risk of a gout attack increases with increasing levels of hyperuricemia. So does the risk of nephrolithiasis (N20.0).

Normal values: up to 7.0 mg/dl in men and 6.0 mg/dl in women, or up to 416 μmol/l in men and up to 357 µmol/l in women; in urine between 0.3 and 0.8 gl/24 h (men) and 0.3 to 0.7 g/24 h in women.

Pathologically decreased: Wilson's disease, AIDS, malignancies, severe liver parenchymal damage, heavy metal intoxications, overmedication with uricosurics, allopurinol and other drugs, tubular kidney disease, xanthinuria.

Pathologically elevated: psoriasis, Lesh-Nyhan syndrome, chronic alcohol consumption, starvation states. Renal insufficiency, after large muscle damage, malignant tumors, leukemias, polycythaemiae vera, primary hyperuricemia, chemotherapy and radiotherapy of tumors, tubular toxins, drugs.

Standard values: up to 7.0 mg/dl for men and 6.0 mg/dl for women, or up to 416 μmol/l for men and up to 357 µmol/l for women; in urine between 0.3 and 0.8 gl/24 h (men) and 0.3 to 0.7 g/24 h for women.

1. Milicevic S et al(2015) Correlation of Parathormone and the Serum Values of Acidum Uricum with Calcium Nephrolithiasis Examined by Three Different Methods of Diagnostics. Acta Inform Med 23:132-134.