Serum Enzymes in Disease

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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 Disease

• Traumatic 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.