Serum Enzymes in Disease

1. Serum Enzymes in Disease Dr. Essam H. Aljiffri

2. 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.

3. 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.

4. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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

14. 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.

15. 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.

16. 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.

17. 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

18. 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.

19. 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.

20. Haematological disorders • Elevated serum LDH activities (owing to increases in HBD) are found in various acquired haematological disorders including: • megaloblastic anaemias and, • leukaemias.

21. 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.