Total lactate dehydrogenase in serum
Apr 20, 2018
Reference values of the activity of total LDH in serum are 208-378 IU / l.
LDG - a glycolytic zinc-containing enzyme that reversibly catalyzes the oxidation of L-lactate to pyruvic acid, is widely distributed in the human body. The greatest activity of LDH is found in the kidneys, heart muscle, skeletal muscles and liver. LDH is contained not only in the serum, but also in a significant amount in erythrocytes, so the serum for the study should be free of traces of hemolysis. Most human organs and tissues contain five isoenzymes of LDH.The nature of the isoenzyme spectrum of LDH and the type of metabolism in the tissue correlate with each other. In tissues with predominantly aerobic metabolism( heart, brain, kidneys), the isoenzymes LDG1 and LDH2 predominate. In tissues with pronounced anaerobic metabolism( liver, skeletal muscle), isoenzymes LDG4 and LDH5 predominate. In the serum of a healthy person, all five isoenzymes of LDH are constantly detected. A regularity is observed with respect to the activity of LDH isoenzymes: the activity of LDH2 & gt; LDH1 & gt; LDH3 & gt; LDH4 & gt; LDG5.Damage to one or another organ changes the isoenzymatic spectrum of blood serum, and these changes are caused by the specific isoenzyme composition of the injured organ.
Increased LDH activity under physiological conditions is observed in pregnant women, newborns, in persons after intensive physical exertion.
The increase in LDH activity in MI is observed 8-10 hours after its onset. After 48-72 hours, a maximum of activity is achieved( the increase is usually 2-4 times), it remains increased for 10 days. These terms may vary depending on the size of the site of the damaged
heart muscle. The increase in the activity of total LDH in patients with MI occurs due to a sharp increase in LDH1 and in part LDH2.In patients with angina pectoris, an increase in LDH activity is not observed, which makes it possible to apply LDH determination within 2-3 days after an anginal attack as a highly reliable criterion for the absence of damage to the heart muscle.
Moderate increase in the activity of total LDH is observed in the majority of patients with acute coronary insufficiency( without MI), myocarditis, with chronic heart failure, with congestive phenomena in the liver. In patients with cardiac arrhythmias, LDH activity is usually normal, but with the use of electropulse therapy, it sometimes increases.
The source of increased LDH activity may be pulmonary tissue in embolism and pulmonary infarction. The combination of normal ACT activity, increased LDH activity and increased bilirubin concentration can serve as a diagnostic triad of pulmonary embolism and for its differentiation from myocardial infarction. In pneumonia, enzyme activity may sometimes not increase.
In myopathies( muscular dystrophy, traumatic muscle damage, inflammatory processes, disorders related to endocrine and metabolic diseases), an increase in LDH activity is observed;With the neurogenic diseases of muscles, LDH activity does not increase.
In acute viral hepatitis, LDH activity in serum increases in the early days of icteric period;with mild and moderate forms of the disease quite quickly returns to normal levels. Heavy forms of viral hepatitis, and especially the development of hepatic insufficiency, are accompanied by a pronounced and longer increase in LDH.
With mechanical jaundice, the LDH activity is normal in the first stages of the obstruction of the bile ducts, at a later stage the LDH activity rises due to secondary liver damage.
In liver carcinomas or cancer metastases, the liver may experience an increase in LDH activity.
In the remission phase of chronic hepatitis and cirrhosis of the liver, LDH activity in the blood remains within normal limits or slightly increased. At an aggravation of the process, an increase in the activity of the enzyme is noted.
Increase in LDH activity is characteristic of megaloblastic and hemolytic anemia, therefore its definition is used for differential diagnosis of Gilbert's disease( LDH in norm) and chronic hemolytic anemia( LDH is increased).
LDH activity increases with acute and exacerbation of chronic kidney disease;in chronic renal diseases associated with uremia, it can be normal, but often increases after hemodialysis, which is due to the removal of enzyme inhibitors during this procedure.