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Cystatin C reflects kidney function 

Cystatin C is a small protein formed in the body’s cells, with the task of inhibiting the breakdown of certain proteins. Cystatin C is filtered and excreted by the kidneys, and measurement of cystatin C is therefore used to assess kidney function.

Brief about cystatin C

  • Cystatin C is a protein formed in almost all of the body’s cells and excreted via the kidneys.
  • By measuring the level of cystatin C in the blood, one can estimate kidney function and health.
  • In contrast to the traditional kidney function marker creatinine, cystatin C is not influenced by age, gender, muscle mass, and diet.

What is cystatin C?

Cystatin C is a small protein formed in all of the body’s cells with a nucleus and is constantly secreted from these cells, as its task includes inhibiting certain enzymes from breaking down proteins outside the cells. Cystatin C is filtered and excreted via the kidneys, and its levels in the blood therefore reflect kidney function.

Unlike the traditional marker for kidney function, creatinine, cystatin C is not influenced by muscle mass, diet, age, or gender. The test is also better at measuring moderately decreased kidney function seen in early kidney damage and better at quickly detecting rapid declines in kidney function.

What are the reference values for cystatin C?

The reference values for cystatin C vary depending on age and may also vary depending on the laboratory performing the analysis.

What does a high value mean?

A high value of cystatin C indicates impaired kidney function, meaning the kidneys are less efficient at filtering and cleansing the blood of waste products. Elevated values may also occur in other medical conditions without impaired kidney function, for example, hyperthyroidism can cause elevated levels of cystatin C. Treatment with cortisone can also lead to elevated levels without impaired kidney function.

What does a low value mean?

A low value is very rare but can occur in connection with diseases such as hypothyroidism.

Why test for cystatin C?

Cystatin C provides a good indication of kidney health, often more reliable than traditional tests like measuring creatinine. Therefore, measuring cystatin C is valuable if kidney conditions are suspected or if one is simply curious about kidney function.

When dosing certain medications and before using contrast agents in X-rays, it is also important to know the kidney function beforehand.

How can I affect my cystatin C levels?

The levels of cystatin C itself do not affect health; elevated or low levels are secondary to other medical conditions affecting kidney health.

Healthy lifestyle habits in general help reduce the risk of kidney diseases. Factors such as quitting smoking, weight loss, regular physical activity, a healthy diet, and maintaining normal blood pressure help the kidneys.

However, many diseases affecting the kidneys arise due to factors beyond one’s control. If one has been affected by kidney disease, it is always valuable to detect and treat the disease as early as possible. Many medications also affect the kidneys, so it may be valuable to discuss kidney health with a doctor when using various medications in general.

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