The functions of the liver consist of:
Storage: glycogen, vitamins (A, D, E, K, B12), metals (iron, copper).
Metabolism of protein (plasma protein synthesis; urea formation; amino acid interconversions - deamination). The albumin synthesis rate is around 12 g per day.
Metabolism of carbohydrate (glycogen synthesis and breakdown; gluconeogenesis).
Metabolism of fat (synthesis of cholesterol, bile acids, lipoproteins, fatty acids and enzymes, e.g. lecithin acyl transferase (LCAT); catabolism of chylomicrons and very low density lipoprotein (VLDL) remnants, low density lipoprotein (LDL) and high density lipoprotein (HDL) (excretion in the bile of cholesterol and phospholipids).
Detoxification and inactivation of hormones (steroid hormone detoxification and conjugation; polypeptide hormone inactivation; 25-hydroxylation of vitamin D), drugs and toxins.
Kupffer cells - part of the reticuloendothelial system.
Hydrogen ion homeostasis: decrease in ureagenesis and increased glutamine synthesis in acidosis.
The serum protein changes that may be associated with liver disease include:
The presence of acute phase reactants: in acute hepatitis;
Reduction in serum albumin;
Release of integral cell membrane enzymes:
Transaminases: aspartate aminotransferase (AST), alanine aminotransferase (ALT)
Bile ductular enzymes: alkaline phosphatase, gamma-glutamyl transferase and 5-nucleotidase
Increased serum immunoglobulins: IgG, IgA, IgM;
Appearance of abnormal protein antigens (marker export proteins): alpha-fetoprotein, ferritin, alpha 1-antitrypsin.
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