Contents
What is alkaline phosphatase?
Alkaline phosphatase is a specific enzyme belonging to the group of hydrolases. It is necessary for the dephosphorylation reactions to successfully take place in the body, namely: the elimination of phosphate from organic substances, which occurs at the molecular level. Carrying phosphorus through the cell membrane, phosphatase has a certain constant concentration in the blood and is an indicator of the norm of phosphorus-calcium metabolism. The name “alkaline” enzyme was received because it exhibits the greatest activity in the presence of a pH of the medium in the range from 8,6 to 10,1.
Although alkaline phosphatase is one of the most common enzymes, its mechanism of action is not fully understood. It is worth noting that in the human body it is present almost everywhere, in all tissues, but it is presented in several varieties: renal, intestinal, placental, hepatic and bone. As for blood serum, in adults, phosphatase is represented by the last two isoenzymes, in relatively equal amounts. In the bones, the enzyme is formed in osteoblasts, and in the liver in hepatocytes. The higher the activity of certain cells, for example, in case of bone fractures or the destruction of liver cells, the higher the level of phosphatase in the blood becomes.
The norm of alkaline phosphatase in the blood
As for the normal level of alkaline phosphatase in the blood, these indications fluctuate in a fairly wide range, they can range from 44 to 147 IU / l. In this case, it is worth paying attention to the gender of the person from whom blood was taken for research, as well as to his age. In pregnant women, this indicator may be slightly overestimated, as well as in adolescents who are in the stage of puberty, but will not indicate any abnormalities in their body. This is simply due to the restructuring of some life support systems, as well as the growth of bone tissue or the placenta.
In addition, the norm indicators may vary depending on the reagents used for its study in various laboratories, since there is no standardized methodology at the moment. Specific figures change, but the range of their fluctuations, nevertheless, remains insignificant, therefore, when determining the norm, one can rely on the following average indicators:
for children under 10 years old – from 150 to 350
for children from 10 to 19 – from 155 to 500
for adults under the age of 50 – from 30 to 120
for the age category from 50 to 75 – from 110 to 135
for people over 75 years old – from 165 to 190
These reference values are given in international units per litre.
Alkaline phosphatase is elevated
A study of an increase or decrease in the level of phosphatase in the blood is carried out according to some indications. This may be preparation for surgery, as well as a routine examination of the patient. They take blood to determine the level of this enzyme and during “liver tests” to assess the functional ability of the organ.
Often, when patients complain of fatigue, loss of appetite, nausea, or pain in the right hypochondrium, the level of alkaline phosphatase in the blood is studied. The result is also indicative for the diagnosis of various lesions of bones and bone tissue.
When alkaline phosphatase is elevated, it almost always means either damage or involvement in any pathological process of either the bones, or the liver, or the biliary tract. Additional studies help to distinguish and clarify the results, so if along with this enzyme there is an overestimation of the level of ALT and AST, then this clearly indicates liver disease. If, in combination with alkaline phosphatase, the level of calcium and phosphorus is increased, then bone tissue damage is evident.
Causes of an increase in alkaline phosphatase
As one or another reason, four main subgroups can be distinguished that lead to an increase in the blood level of this enzyme:
The first group is disorders associated with changes or diseases of the liver. This may be obstructive jaundice, which is caused by obstruction of the biliary tract, stones located in the bile ducts, as well as the occurrence of scars in them after operations. Cancer of either the head of the pancreas, or the stomach, or the liver with metastases. With hepatitis of any origin, an increase in phosphatase is observed, as well as with cirrhosis. Another viral infection, namely infectious mononucleosis, can cause liver dysfunction, and as a result, an increase in this enzyme in the blood.
The second group is disorders associated with changes in bone tissue. These include diseases such as osteomalacia (softening of bone tissue due to calcium deficiency), osteosarcoma, metastases affecting bone tissue, Paget’s disease (abnormal growth of bones with a change in their structure), fractures, rickets and multiple myeloma.
The third group is other reasons. A jump in alkaline phosphatase levels can be associated with myocardial infarction, with ulcerative colitis and intestinal perforation, as well as with hyperparathyroidism (a hormonal disease characterized by calcium leaching from the bones).
The fourth group is conditions that are not associated with diseases, but are caused by a number of factors. This includes pregnancy, adolescence, healthy women under 20 and healthy men under 30, as well as the use of antibiotics and hormonal drugs for contraception and a number of other drugs that are included in a rather extensive list and contains up to 250 items. Also, if the blood was refrigerated after it was taken for analysis, the level of alkaline phosphatase will be too high.
It should be noted that an increase in the level of this enzyme is not in all cases without exception an indicator of a particular disease. Sometimes it can exceed the norm even in absolutely healthy people. Therefore, in order to judge the presence of a particular pathological process, it is necessary to conduct additional studies and study the results obtained as a whole.
Alkaline phosphatase is lowered
Attention should be paid to a decrease in this enzyme in the blood, since such an indicator can serve as signs of a number of diseases that are no less dangerous than with an increase in the level of phosphatase.
Possible reasons that lead to a decrease in the level of the enzyme:
Massive blood transfusions.
Decreased functionality of the thyroid gland.
Anemia of severe severity.
Deficiency in the body of elements such as magnesium and zinc.
A rare disease, hypophosphatasia, is congenital and causes the bone tissue to soften.
In pregnant women, a decrease in alkaline phosphatase can be a sign of placental insufficiency.
So, in order to qualitatively evaluate the result of an increase or decrease in the level of alkaline phosphatase in the blood, any specialist will need to conduct additional studies. It is worth remembering that the boundaries within which normal phosphatase values can be quite extensive and significantly depend on the age of the subject. Therefore, even a doctor cannot accurately diagnose the presence of a particular disease only with an increase in the level of this enzyme. Nevertheless, this indicator, together with additional studies, can give a complete picture of the disease.