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Serum Enzymes in Disease

Dr. Essam H. Aljiffri

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Myocardial Infarction

• Necrosis of the myocardium leads to the release into the circulation of tissue enzymes, particularly; CK, AST and LDH (HBD), these are released from the heart and cleared from the circulation at different rates.

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Myocardial Infarction

• The first to rise is CK, activities being raised within 6 h of myocardial infarction.

• Total CK reaches a peak at 24-36 h, slightly later than the maximum activity of CK-MB isoenzyme.

• In uncomplicated cases, CK returns to normal in 3 days.

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Myocardial Infarction

• Serum AST rises more slowly, reaching a maximum activity at about 48h and returning to normal in 4-5 days.

• No significant elevations in HBD are seen for the

first 24 h; values reach a maximum at about 3 days and remain elevated for up to 8 days.

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Myocardial Infarction

• CK and HBD are useful indicators of myocardial infarction, and are more specific than AST.

• CK from skeletal muscle may be raised following an intramuscular injection, chest compression for resuscitation or electrical defibrillation.

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Muscle Disease

• Skeletal muscle is a rich source of several enzymes including CK, AST, ALT, aldolase and LDH.

• The measurement of total CK activity is the most widely used enzyme in the investigation of muscle damage.

• This being increased most frequently and showing the highest activities in diseases particularly muscular dystrophies.

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Muscle Disease

Muscular Dystrophy

The muscular dystrophies are a group of genetically determined disorders of muscle.

Duchenne muscular dystrophy is an X-linked recessive disorder caused by an abnormal dystrophin gene and characterized by progressive weakness of muscles from the age of 5 years.

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Muscle Disease

Muscular Dystrophy

• Raised serum CK activities occur before the onset of clinical symptoms and values greater than 10 times the upper limit of normal.

Becker's muscular dystrophy is a form of muscular dystrophy, affected males sometimes reaching reproductive age.

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Muscle Disease

Toxic Myopathies

• Many drugs and chemicals may produce local or generalized muscle damage.

• Intramuscular injections may cause muscle damage by two mechanisms, trauma and effect of the agent being injected.

• The latter may be caused by analgesics, a possible cause of elevated CK activity which should be considered in cases of suspected myocardial infarction.

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Muscle Disease

Malignant Hyperpyrexia

• Malignant hyperpyrexia is a serious toxic myopathy, this usually follows general anaesthesia and in some cases have been described after the administration of muscle relaxants.

• High serum CK activities are seen during attacks.

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Muscle DiseaseTraumatic Myopathies

• Causes of trauma to muscles in release of enzymes include surgery, intramuscular injections and post-exercise changes.

• Serum CK values usually return to normal within 48 h of a single intramuscular injection.

• Vigorous exercise of short duration and prolonged moderate exercise may produce elevations in serum CK, particularly in untrained athletes.

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Liver Disease

• One of the transaminases is used as an indicator of hepatocellular damage, ALT being more specific for this purpose than AST.

• Increase synthesis of alkaline phosphatase and GGT in biliary cells are seen in cholestasis

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Bone Disease

• ALP Level usually very high in Paget's disease of the bone (greater than 10 times the upper limit of normal).

• Both primary and secondary bone tumours can cause increases in alkaline phosphatase, typically up to five times the upper limit of normal.

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Enzymes in Urine

• Enzymes appear in urine from two sources:• by filtration of plasma and,• by leaking from cells lining the urinary tract.

• Amylase is normally detected in urine, while other serum enzymes are too large to cross the glomerulus.

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Enzymes in Urine

• Several enzymes derived from renal tubular cells have been investigated as indicators of tubular damage, particularly:

alkaline phosphatase N­acetyl-beta-glucosaminidase (NAG), ALT and,GGT.

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Haematological disorders

• Red cell enzymes activities may be abnormal because of an inherited deficiency or due to acquired disease.

• Many inherited defects such as: haemolytic disease, spherocytosis or, methaemoglobinaemia

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Haematological disorders

• Genetic examples due to defective enzyme activity of glucose-6-phosphate dehydrogenase (G6PD).

• Synthesis of G6PD is controlled by an X-linked gene and therefore males predominantly are affected.

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Haematological disorders

• Haemolytic anaemia may also be caused by other enzyme defects including those affecting:

pyruvate kinase, glutathione synthetase, hexokinase and, enzymes of the glycolytic pathway.

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Haematological disorders

• Elevated serum LDH activities (owing to increases in HBD) are found in various acquired haematological disorders including:

megaloblastic anaemias and, leukaemias.

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Tissue Enzymes

• The estimation of tissue enzymes is usually in the investigation of inherited metabolic diseases, often being done on biopsy specimens from specific tissues.