Selected blood values: Liver values | Blood test

Selected blood values: Liver values

A wide variety of blood tests can be summarized under the so-called liver values. In a narrower sense, liver values are two enzymes with long names: aspartate aminotransferase (AST, ASAT, or known as GOT for glutamate oxaloacetate transaminase) and alanine aminotransferase (ALT, ALAT, or known as GPT for glutamate pyruvate transaminase). AST and ALT are also briefly summarised together as transaminases and are usually determined simultaneously.

Both enzymes occur in all cells of the body, but are most concentrated in the liver. This is the reason for the diagnostic importance of transamniases. When liver cells are damaged, the corresponding enzymes enter the bloodstream and can be determined from there.

An increase in the number of transamniases can therefore provide an indication of liver damage. The advantage of this is that the values often increase even with slight damage to the liver and thus have a high diagnostic weight. Common causes for increased liver values are heavy alcohol consumption or the intake of medication.

Other important causes are inflammation of the liver (hepatitis), which can be caused by viruses, for example, but also hereditary diseases such as hemochromatosis or Wilson’s disease, which lead to damage to the liver tissue. Elevated transaminases can also be found in liver cirrhosis and liver cancer. However, it should be noted that in liver cirrhosis the transaminases are often almost within the normal range, or may even fall below it if a large part of the liver tissue has already been destroyed and replaced by connective tissue. It is also important to note that although increases in AST and ALT are very often caused by problems in the liver, this does not always have to be the case. Disturbing factors can be, for example, heavy physical activity, muscle or even heart disease, which can also lead to an increase in values.

Vitamin D (Calcitriol)

Vitamin D can be absorbed in its precursors from food and then converted into the active vitamin D (calcitriol) in the liver and kidneys through chemical changes. However, a large part of it is also formed from a precursor of cholesterol in human skin under the influence of UV light. The active vitamin D has the function of a messenger substance (hormone) in the body, which is decisively involved in the regulation of the body’s own calcium balance.

If the concentration of vitamin D in the blood rises, the calcium concentration also increases. This can be explained by the fact that calcitriol causes an increased absorption of calcium from food in the intestine. It promotes the formation of bone substance.

The determination of Calcitriol is one of the less frequently performed blood tests. Its use is limited to a few useful occasions. These are always diseases that affect the calcium balance.

These are bone or kidney diseases and diseases of the parathyroid gland. In the case of bone diseases, the question of a possible causal vitamin D deficiency is in the foreground. In the case of kidney diseases, calcitriol plays a role because its formation itself depends on the function of the kidneys.

If the kidney function is disturbed (renal insufficiency), the calcitriol levels are therefore lower. The importance of vitamin D in suspected parathyroid disease is due to the fact that the so-called parathyroid hormone is produced in these organs. Since parathormone also has an influence on the blood calcitriol concentration, the determination of calcitriol can be diagnostically useful in certain parathyroid diseases.