Encyclopedia of Health and Medicine

74 The Gastrointestinal System
levels suggest liver dysfunction. The normal range
of serum albumin is 3.4 to 5.4 grams per deciliter
(g/dL).
Bilirubin One key function of the liver is to
complete the break down of old erythrocytes (red
blood cells) to recycle their ingredients for other
uses in the body. The SPLEEN initiates this process,
splitting the HEMOGLOBIN erythrocytes contain into
its core proteins, heme and globin, and extracting
the pigment bilirubin from the heme. Bilirubin is
a waste product that the liver chemically alters to
use in synthesizing BILE. The chemically processed
bilirubin is conjugated or direct bilirubin; bilirubin
that circulates in the blood is unconjugated or
indirect bilirubin.
A healthy liver excretes most of the conjugated
bilirubin it produces in the bile. A damaged liver
cannot keep up the pace of bile production, allowing
conjugated bilirubin to escape into the blood.
Elevated circulation of conjugated, or direct,
bilirubin suggests liver or GALLBLADDER dysfunction.
The normal range of serum direct bilirubin is
0.0 to 0.4 milligrams per deciliter (mg/dL).
Enzymes Enzymes are catalytic substances that
expedite chemical processes within the liver. In a
healthy liver enzymes remain within the lobules,
the working communities of hepatocytes. Hepatocytic
damage results in enzymes leaking from the
cells and spilling out into the blood. The commonly
measured liver enzymes are
• the aminotransferases (also called transaminases),
which catalyze amino acid METABOLISM—
for example, aspartate aminotransferase (AST),
also called serum glutamic oxaloacetic transaminase
(SGOT), and alanine aminotransferase
(ALT), also called serum glutamic pyruvic
transaminase (SGPT)
LIVER FUNCTION BLOOD TESTS
Blood Test Normal Values Liver Implications of Abnormal Findings
ALBUMIN 3.4 to 5.4 grams per deciliter (g/dL) decreased level may suggest hepatocellular
necrosis, HEPATITIS, CIRRHOSIS
alkaline phosphatase (ALP) 44 to 147 International Units per liter (IU/L) elevated level may suggest hepatitis, cirrhosis,
biliary obstruction, LIVER DISEASE OF ALCOHOLISM
alanine aminotransferase 20 to 125 IU/L elevated level may suggest hepatocellular
(ALT)/serum glutamic pyruvic
necrosis, hepatitis, cirrhosis, HEPATOTOXINS
transaminase (SGPT)
aspartate aminotransferase 10 to 34 IU/L elevated level may suggest hepatocellular
(AST)/serum glutamic
necrosis, hepatitis, cirrhosis, LIVER CANCER,
oxaloacetic transaminase
liver disease of alcoholism
(SGOT)
direct BILIRUBIN 0.0 to 0.4 g/dL elevated level may suggest hepatitis, cirrhosis,
biliary obstruction, gallstones, GALLBLADDER
DISEASE, CHOLESTASIS
gamma-glutamyltranspeptidase 0 to 51 IU/L elevated level may suggest hepatitis, cirrhosis,
(GGT)
liver cancer, cholestasis, hepatocellular
necrosis, hepatotoxins
prothrombin time (PT) 11 to 13.5 seconds delayed time may suggest hepatitis, cirrhosis,
gallstones, biliary occlusion