Laboratory value alkaline phosphatases – too high, too low or normal?

You can find out what alkaline phosphatases are and when the laboratory value is increased or decreased here.

Abstract

• Alkaline phosphatases are enzymes that split phosphate groups of molecules.
• There are 15 different alkaline phosphatases.
• The normal values are strongly dependent on age and gender.
• The AP value is considered an indicator for various diseases of the liver and skeleton.

What are alkaline phosphatases?

Alkaline phosphatases, also known as AP or ALP, are a group of cytoplasmic enzymes. There are different subgroups of alkaline phosphatases, which are named after the tissue in which they are predominantly found. They cleave phosphate groups from molecules, but their full role in metabolism is not yet fully understood. The highest activities of AP are known in the small intestine, bones, liver, bile ducts, kidneys and placenta.

The value of alkaline phosphatases is taken from the blood serum and is considered an indicator of liver diseases, diseases of the bile ducts and changes in bone metabolism. The AP contained in the plasma originates mainly from the liver and bones.

When is the laboratory value determined?

• For suspected bone tumors
• If bone metastases are suspected
• If liver disease is suspected

The value is taken from the blood serum and it is analyzed for all subgroups of alkaline phosphatases.

What are normal values?

The following values are for guidance only. The results may vary between different laboratories. You should therefore always discuss your results with a doctor.

* U/l = units per liter

When is alkaline phosphatase low?

It is rather rare for the value to be lowered. If this is nevertheless the case, there may be various causes:

• Pronounced hypothyroidism
• Anemia
• Wilson’s disease (rare hereditary disease)
• Achondroplasia (rare hereditary disease)
• Hypophosphatasia (rare hereditary disease)

When is alkaline phosphatase elevated?

An elevated AP value is much more common than a low one. There are various causes for an AP concentration above the normal value:

• Liver diseases such as tumors, hepatitis, bile congestion or bile duct inflammation
• Bone diseases such as bone tumors, Paget’s disease, rickets(vitamin D deficiency)
• Certain forms of kidney weakness (renal insufficiency)
• Acromegaly (excess growth hormone) and Cushing’s syndrome
• Parathyroid hyperfunction
• Taking various medications (allopurinol, antiepileptic drugs, contraceptive pill)

However, there are also situations in which an increased AP value has no pathological cause. A higher AP concentration is normal during fetal growth and during pregnancy.

Sources

• https://flexikon.doccheck.com/de/Alkalische_Phosphatase
• https://www.netdoktor.de/laborwerte/alkalische-phosphatase/
• https://www.internisten-im-netz.de/mediathek/blutbild-erklaerung/alkalische-phosphatase.html