Originally described in infants, transient hyperphosphatasemia can also occur in adults and during pregnancy. Ī condition that can result in significantly increased plasma ALP is benign transient hyperphosphatasemia. Of these four, PLALP and GCALP are the most heat stable at 65 C, and the bone ALP component of TnALP is the least. In healthy, non-smoking individuals, the PLALP and GCALP represent less than 1% of total ALP activity in the serum. There are four isozymes: placental ALP or hPLALP (human placental ALP), germ cell ALP (GCALP or PLALP-like), intestinal ALP (IALP), and tissue-nonspecific ALP (TNALP). Īlkaline phosphatase is part of a family of zinc metalloenzymes that are highly concentrated in the microvilli of the bile canaliculus as well as several other tissues (e.g., bone, intestines, and placenta). They also correlate with obesity with a normal reference range higher in those with higher body mass index. Hepatocellular injury and not necessarily cell death triggers the release of these enzymes into circulation. Both AST and ALT values are higher in normal males than females. ALT is usually higher than AST in most types of liver disease in which the activity of both enzymes is predominantly from the hepatocyte cytosol. The half-life of ALT is approximately 47 ± 10 hours. ĪLT is a cytosolic enzyme that is found in high concentrations in the liver. It is not as sensitive or specific for the liver as ALT, and elevation in AST may be seen as secondary to nonhepatic causes as well. AST activity in neonates and infants is approximately twice that in adults, but these decline to adult levels by approximately six months. AST is present as cytosolic and mitochondrial isoenzymes and is found in the liver, cardiac muscle, skeletal muscle, kidneys, brain, pancreas, lungs, leucocytes, and red cells. They participate in gluconeogenesis by catalyzing the transfer of amino groups from aspartic acid or alanine to ketoglutaric acid to produce oxaloacetic acid and pyruvic acid, respectively. They are markers of hepatocellular injury. The actual function of the liver can be graded based on its ability to produce albumin as well as vitamin K-dependent clotting factors.Īminotransferase includes AST and ALT. An R ratio of >5 is defined as hepatocellular, <2 is cholestatic, and 2–5 is a mixed pattern. The R ratio is calculated by the formula R =(ALT value÷ALT ULN)÷(alkaline phosphatase value÷alkaline phosphatase ULN). The R ratio has been used to assess whether the pattern of liver injury is hepatocellular, cholestatic, or mixed. Isolated hyperbilirubinemia is defined as an elevation of bilirubin with normal alkaline phosphatase and AST/ALT levels. A mixed injury pattern is defined as an elevation of alkaline phosphatase and AST/ALT levels. An elevation in ALP and bilirubin in disproportion to ALT and AST would characterize a cholestatic pattern. Elevations in ALT and AST in out of proportion to ALP, and bilirubin denotes a hepatocellular disease. The term 'liver function tests 'is a misnomer as many of the tests do not comment on the function of the liver but rather pinpoint the source of the damage. These tests can help determine the area of hepatic injury, and the elevation pattern can help organize a differential diagnosis. Typically when reviewing liver function tests, the discussion includes alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), 5'nucleotidase, total bilirubin, conjugated (direct) bilirubin, unconjugated (indirect)bilirubin, prothrombin time (PT), the international normalized ratio (INR), lactate dehydrogenase, total protein, globulins, and albumin.

The liver also plays a significant role in metabolism, regulation of red blood cells (RBCs), and glucose synthesis and storage. The liver, located in the right upper quadrant of the body and below the diaphragm, is responsible for several functions, including primary detoxification of various metabolites, synthesizing proteins, and producing digestive enzymes.

Vivaldi variation