Liver enzymes Flashcards
(48 cards)
Bilirubin is a breakdown product of heme (ferroprotoporphyrin IX).
The initial steps of bilirubin metabolism occur in reticuloendothelial cells, predominantly in the spleen.
normal values of total serum bilirubin
are between 1.0 and 1.5 mg/dL, with 95% of a normal population falling between 0.2 and 0.9 mg/dL.
Normal values for the indirect component are
between 0.8 and 1.2 mg/dL.
The most frequently reported upper limit
of normal for conjugated bilirubin is 0.3 mg/dL.
The presence of conjunctival icterus
suggests a total serum bilirubin level of at least 3.0 mg/dL but does not allow differentiation between conjugated and unconjugated hyperbilirubinemia.
Tea- or cola-colored urine may indicate the presence of bilirubinuria and thus conjugated hyperbilirubinemia.
the most sensitive markers of acute hepatocellular injury,
The serum aminotransferases (also called transaminases),
ALT (formerly serum glutamic pyruvic transaminase, or SGPT)
AST (formerly serum glutamic oxaloacetic transaminase, or SGOT) catalyze the transfer of the α-amino groups of alanine and l-aspartic acid, respectively, to the α-keto group of ketoglutaric acid.
a cytosolic enzyme also found in many organs, is present in greatest concentration by far in the liver and is, therefore, a more specific indicator
ALT
The differential diagnosis of marked elevations of aminotransferase levels (>1000 U/L)
includes viral hepatitis (A to E), toxin- induced liver injury, DILI, ischemic hepatitis, and less commonly, autoimmune hepatitis, acute Budd-Chiari syndrome, ALF caused by Wilson disease, and acute obstruction of the biliary tract.
If the AST level is less than 300 U/L, a ratio of AST to ALT of more than 2 suggests
alcohol- associated liver disease, and a ratio of more than 3 is highly suggestive of alcohol-associated liver disease
ratio results from a deficiency of pyridoxal 5′-phosphate in patients with alcohol- associated liver disease;
ALT synthesis in the liver requires pyridoxal phosphate
When a patient with chronic alcohol-associated liver disease sustains a superimposed liver injury, particularly acetaminophen hepatotoxicity,
the aminotransferase levels can be strikingly elevated, yet the AST/ ALT ratio is maintained.
CHRONIC, MILD ELEVATIONS, ALT > AST (<150 U/L OR 5 × NORMAL)
Hepatic α1-Antitrypsin deficiency Autoimmune hepatitis Chronic viral hepatitis (B, C, and D) Hemochromatosis Medications and toxins Steatosis and steatohepatitis Wilson disease
Nonhepatic
Celiac disease
Hyperthyroidism
SEVERE, ACUTE ELEVATIONS, ALT > AST (>1000 U/L OR > 20-25 × NORMAL)
Hepatic
Acute bile duct obstruction
Acute Budd-Chiari syndrome Acute viral hepatitis Autoimmune hepatitis
Drugs and toxins
Hepatic artery ligation Ischemic hepatitis Wilson disease
SEVERE, ACUTE ELEVATIONS, AST > ALT (>1000 U/L OR >20-25 × NORMAL)
Hepatic
Medications or toxins in a patient with underlying alcohol-associated liver injury
Nonhepatic
Acute rhabdomyolysis
Chronic, mild elevations, AST > ALT (<150 U/L, <5 × normal)
Hepatic
Alcohol-associated liver injury (AST/ALT >2:1, AST nearly always <300 U/L)
Cirrhosis
Nonhepatic
Hypothyroidism
Macro-AST Myopathy Strenuous exercise
The first step in the evaluation of mildly elevated serum aminotransferase levels
is to repeat the test to confirm persistence of the elevated value.
The clinical onset of Wilson disease
is usually between 3 and 55 years of age; the diagnosis should be considered initially in all patients age 40 or younger and those older than age 40 with aminotransferase elevations that remain unexplained after other causes are excluded
has a serum half-life of approximately 7 days, and although the sites of degradation are unknown,
ALP
clearance of ALP from serum is independent of either patency of the biliary tract or functional capacity of the liver
In a person with isolated elevation of the serum ALP level,
the serum GGTP or 5′NT is used to distinguish a liver from a bone origin of the ALP elevation
elevated serum GGTP level
has high sensitivity for hepatobiliary disease, its lack of specificity limits its clinical utility
GGTP is elevated in patients
taking antiepileptics, including phenytoin, carbamazepine, valproic acid, and barbiturates, as well as some drugs used in antiretroviral therapy, such as non-nucleoside reverse transcriptase inhibitors and the protease inhibitor abacavir.
PBC is a classic autoimmune disease.
immunologic injury is characterized by T cell–mediated destruction of the intrahepatic bile ducts.
Although predominantly a disease of middle- aged women, with a median age at diagnosis of approximately 50 years, 5% to 10% of affected patients are men.
Albumin
The average adult pro- duces approximately 15 g/day and has 300 to 500 g of albumin distributed in body fluids.
The liver has the ability to double the rate of synthesis in the setting of rapid albumin loss or a dilutional decrease in the serum albumin concentration
half-life of albumin is 14 to 21 days; there are multiple sites of degradation, including skin, muscle, liver, and kidney, as well as leakage in the gut.
Bland cholestasis
Anabolic steroids
Estrogens
Cholestatic hepatitis
Angiotensin-converting enzyme inhibitors: captopril, enalapril Antimicrobials: amoxicillin-clavulanic acid, ketoconazole Azathioprine
Chlorpromazine
NSAIDs: sulindac, piroxicam
