Page 2636 - Cote clinical veterinary advisor dogs and cats 4th

1346 Gamma-Glutamyl Transferase (GGT) Gastrin

Gamma-Glutamyl Transferase (GGT)
VetBooks.ir Definition Pearls

(if hyperbilirubinemia absent); abdominal
Serum enzyme, marker for liver disease associ- transaminase (ALT), and bilirubin; bile acids • GGT is more sensitive but less specific for
ated with cholestasis or biliary hyperplasia ultrasound +/− liver biopsy. liver disease than ALP in the cat and more
specific but less sensitive in the dog. However,
Synonyms Important Interspecies Differences the combination of minimal or no increase
GGT, gamma-glutamyltransferase • Serum GGT is significantly increased within in GGT and significant increase in ALP is
24 hours of suckling in pups (not kittens); associated with hepatic lipidosis in the cat.
Physiology levels fall to within reference intervals by 10 • Uncommon cause of increased GGT is
Membrane-associated enzyme present in most days of age. neoplasia (hepatic, pancreatic, renal).
cell types. Greatest activity found in biliary and • Elevated GGT activity generally considered • Increased urine GGT/creatinine ratio has
renal tubular epithelial cells. Increased serum to have better diagnostic sensitivity than ALP been associated with renal disease in dogs and
concentration is primarily associated with for cholestasis in horses and cattle. ponies, but could also be caused by decreased
biliary and hepatic disease. Increased urine GFR.
GGT/creatinine ratio can provide evidence Drug Effects
for renal tubular damage. Corticosteroids cause elevated GGT activity in AUTHOR: Carrie L. Flint, DVM, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
dogs. May see mild elevation with phenobarbital
Reference Interval use.
Dogs: 0-13 U/L; cats: 0-6 U/L
Lab Artifacts
Causes of Abnormally High Levels Variable effects of hemolysis depending on assay
Cholestasis, biliary hyperplasia, ingestion of type (can falsely increase or falsely decrease
colostrum in neonates (some species); may results)
be induced by corticosteroid administration
in dogs. Specimen Collection and Handling
Serum (red-top tube); separate as soon as
Next Diagnostic Steps to Consider possible, store at 8°C
if Levels Are High
• Evaluate recent drug administration. Relative Cost: $ (as individual test); often
• Interpret in light of serum chemistry profile, included in chemistry profiles
including alkaline phosphatase (ALP), alanine

Gastrin

Definition Causes of Abnormally High Levels Drug Effects
Group of peptide hormones secreted by G cells Excess secretion associated with gastric mucosa Increased: H 2 blockers, antacids, and proton
of gastric antrum and duodenum in response hypertrophy, gastric and duodenal ulceration. pump inhibitors
to protein meal. Gastrin stimulates parietal cell The underlying cause is typically a neoplasm of
secretion of gastric acid and histamine release by pancreatic islet delta cells (gastrinoma); when Specimen Collection and Handling
enterochromaffin cells. Also stimulates pancre- these cells undergo neoplastic transformation, Gastrin is not stable at room temperature.
atic acinar cells when bound to cholecystokinin. they regain the ability to produce gastrin Separate serum from clot as soon as possible
(normally only occurs in delta cells of the and transfer from a red top tube to a plastic
Synonyms fetus). Renal failure leads to gastrin accumula- tube. Freeze immediately and ship on dry ice.
G-34 (big gastrin), G-17 (little gastrin), G-14 tion that can cause gastrointestinal ulcer and 1 mL of serum, minimum.
(mini gastrin) upset. Other gastrointestinal disorders may
cause excess gastrin (e.g., upper gastrointestinal Relative Cost: $$
Physiology obstruction, previous small intestine resec-
Ingestion of protein meal stimulates release. tion, gastric dilatation/volvulus, Helicobacter Pearls
Binds to receptors in parietal, enterochromaffin pylori). • Send out test to specialized gastrointestinal
cells, regulating gastric acid release for protein laboratories.
digestion. Enhances digestion by stimulating Next Diagnostic Steps to Consider • The recommended cutoff value for diagnosis
gastric blood flow, antral motility, and pancreatic if Levels Are High of gastrinoma is 10 times the upper limit of
secretion. Stimulates DNA, RNA production, and Evaluate gastric mucosa (endoscopy) for the reference interval.
proliferation of parietal cells and gastric mucosa. hypertrophy, ulceration; assess for pancreatic
islet (delta cell) tumor (abdominal ultrasound AUTHOR & EDITOR: Lois Roth-Johnson, DVM, PhD,
Reference Interval or CT and, with a pancreatic mass or liver DACVP
Overnight fasting sample: less than 27.8 ng/L lesions suggestive of metastases, laparotomy).
Normal dogs may have undetectable
concentrations.

www.ExpertConsult.com