Liver function test

Tishk International University

Medical Analysis

Dr. Rundk A. Hwaiz

The Function of Liver

• Liver is a multifunctional organ that is involved in diverse

body functions.

1. Metabolic Functions

• Liver actively participates in carbohydrate,

lipid, protein, mineral and vitamin metabolisms.

2. Excretory Functions

• Bile pigments, bile salts and cholesterol are

excreted in bile into intestine.

3. Protective functions & detoxification

• Kupffer cells of liver perform phagocytosis to

eliminate foreign compounds.

• Clearance of hormones such as insulin,

parathyroid hormone, oestrogen, cortisol.

4. Synthetic functions

• Synthesis of plasma proteins (albumin and

prothrombin), hormones e.g angiotensinogen,

insulin- like growth factor and triiodothyronine.

5. Storage functions

• Glycogen, vitamins A, D and B12

Liver function tests

• Noninvasive method of screening for the presence of liver

dysfunction

• Pattern of lab test abnormality allows recognition of general

type of disorder

• To assess the severity and occasionally allow prediction of

outcome

• To follow the course of the disease, evaluate response to

treatment, and adjust treatment when necessary

Clinical Lab tests Liver Function Test (LFT)

Markers of Hepatocellular damage (Transaminases)

• AST(Aspartate amino transferase)

• Found in many sources, including liver, heart, muscle,

intestine, RBCs (not specific)

• Elevated in liver diseases, myocardial infarction, muscle

disease.

• ALT(Alanine aminotransferse)

• Found primarily in hepatocytes (specific)

• Elevated in liver diseases

• Normal levels depend on the reference range which actually

differs lab to lab

Markers of Cholestasis

• ALP (Alkaline phosphatase) Enzyme:

• It is found in liver, bone and to lesser extent in placenta,

kidneys, intestines.

• Hepatic ALP present on surface of bile duct epithelia and

accumulating bile salts increase its release from cell surface.

• Associated with hyperbilirubinemia in cholestatic disorders

(Extrahepatic, Intrahepatic)

• Also increased in bone disease (not specific).

• Reference Ranges: Adult: 30-120 U/L Children: up to 360

U/L

Markers of Cholestasis

• GGT (Gammaglutamyl transferase):

• Found in hepatocytes and biliary epithelial cells

• Can confirm hepatic source for a raised ALP.

• Increased also in chronic alcoholism.

• Normal range 6-19 IU/L

Types of bilirubin

• Direct bilirubin: is conjugated (water soluble bilirubin) in

aqueous solution it reacts rapidly with reagent (direct

reacting). Reference range: 0.0-0.2 mg/dL.

• Indirect bilirubin: is unconjugated (water insoluble

bilirubin) because it is less soluble in it reacts more slowly

with reagent (reaction carried out in methanol). Reference

range: 0.2 -0.8 mg/dL.

• Total bilirubin = D+ ID. Reference range: 0.2 – 1.0

mg/dL.

Urine Bilirubin

• Unconjugated bilirubin: water insoluble, binds to albumin

in serum & not filtered by kidneys.

• Conjugated bilirubin: water soluble, filtered by the kidney.

Any bilirubin in urine is conj. bilirubin.

Hyperbilirubinemia causes Jaundice

Joundice is Jaundice Yellow color of skin, nail beds & sclera

caused by deposition of bilirubin secondary to increased

bilirubin levels in blood (hyperbilirubinemia) JAUNDICE IS

NOT A DISEASE HOWEVER, IT IS A SIGN OF AN

UNDERLYING DISEASE

Types of Jaundice

1- Hemolytic Jaundice

2- Obstructive Jaundice

3- Hepatocellular Jaundice

Hemolytic anemia:

Unconjugated hyperbilirubinemia

• Hemolysis

• Hemolytic disease of the newborn

Hepatocellular Jaundice:

• Liver damage (by hepatitis or hepatitis)

Obstructive Jaundice

• In bile duct obstruction

Synthetic Function

Albumin:

• Decreased in chronic liver diseases

• not specific for liver disease

• Decreased also in malnutrition, nephrotic syndrome, protein

losing entropathy

• Reference ranges: 3.5-5.5 g/dl

Prothrombin time (PT):

• Prolonged in severe hepatocellular disease (↓ synthesis) and

cholestatic liver diseases (vit K deficiency).

• To differentiate: in vit K deficiency, injection of vit K

corrects prolonged PT .

Abnormal Patterns

• Elevations in ALT & AST only: suggests cellular injury.

• Elevations in ALP, GGT & Bilirubin: suggests cholestasis or

obstruction.

• Decreased Albumin in chronic liver diseases.