Facts on File Encyclopedia of Health and Medicine

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 SPLEENinitiates this process,
splitting the HEMOGLOBINerythrocytes 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, allow-
ing conjugated bilirubin to escape into the blood.

Elevated circulation of conjugated, or direct,

bilirubin suggests liver or GALLBLADDER dysfunc-

tion. 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. Hepato-

cytic damage results in enzymes leaking from the

cells and spilling out into the blood. The com-

monly measured liver enzymes are

• the aminotransferases (also called transami-
  nases), which catalyze amino acid METABOLISM—
  for example, aspartate aminotransferase (AST),
  also called serum glutamic oxaloacetic transam-
  inase (SGOT), and alanine aminotransferase
  (ALT), also called serum glutamic pyruvic
  transaminase (SGPT)

74 The Gastrointestinal System

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