💧 Renal🟢 BasicUric Acid Metabolism

Uric Acid Metabolism and Gout

How the body makes and clears uric acid, the end product of purine breakdown, and how its excess causes gout.

Key points

Uric acid is the final product of the breakdown of purine bases in humans, because we lack the enzyme uricase that would break it down further.
Most uric acid is filtered and then largely reabsorbed by the kidney, so both overproduction and reduced excretion can raise its blood level.
When the blood uric acid is high, monosodium urate crystals can deposit in joints and trigger the acute inflammation of gout.
Classic gout affects the joint at the base of the big toe (podagra), and long-standing disease forms chalky deposits called tophi.
Enzyme defects such as in Lesch-Nyhan syndrome, and high cell turnover as in leukaemia, raise purine breakdown and uric acid.

Memory trick

Purines end as uric acid (no uricase in humans); a high level makes urate crystals and gout (big-toe podagra, tophi); worse with Lesch-Nyhan and high cell turnover.

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💧 Renal🟢 BasicUric Acid Metabolism

Uric Acid Metabolism and Gout

How the body makes and clears uric acid, the end product of purine breakdown, and how its excess causes gout.

Key points

Uric acid is the final product of the breakdown of purine bases in humans, because we lack the enzyme uricase that would break it down further.
Most uric acid is filtered and then largely reabsorbed by the kidney, so both overproduction and reduced excretion can raise its blood level.
When the blood uric acid is high, monosodium urate crystals can deposit in joints and trigger the acute inflammation of gout.
Classic gout affects the joint at the base of the big toe (podagra), and long-standing disease forms chalky deposits called tophi.
Enzyme defects such as in Lesch-Nyhan syndrome, and high cell turnover as in leukaemia, raise purine breakdown and uric acid.

Memory trick

Purines end as uric acid (no uricase in humans); a high level makes urate crystals and gout (big-toe podagra, tophi); worse with Lesch-Nyhan and high cell turnover.

All of Biochemistry More Renal