AST, ALT, GGTP And Alkaline Phosphatase In Dogs’ And Cats’ Livers

“ALT” stands for alanine transaminase, an enzyme present in the cells of mammalian livers. While the enzyme may also be found in a few other organs, the quantities are low enough to make ALT reasonably liver-specific. The same enzyme is also known by an older name, SGPT, which stands for serum glutamic pyruvic transaminase. Normal serum level of ALT in dogs should be between 12 and 118.

Some canine liver problems can be diagnosed by blood and urine tests.
Some canine liver problems can be diagnosed by blood and urine tests.

ALT is known as a “leakage enzyme,” meaning the cells that contain it must die in order for it to be released. Therefore, if serum ALT levels are up, some death of liver cells has occurred. However, it is important to recognize that there is not a direct correlation among the elevation of the enzyme, the amount of liver damage and the prognosis for the patient. However, trends may be followed that give an indication of improvement or worsening of liver disease.

Many diseases may affect ALT, as well as non-liver conditions. For example, congestive heart failure (CHF) may result in poor blood circulation, causing stagnation of liver blood flow and poor liver function. Some medications, most notably phenobarbital used for seizure control.

“AST” stands for aspartate transaminase, which is also an enzyme. The older name is “SGOT,” which stands for serum glutamic oxaloacetic transaminase. AST is also present in the liver and several other organs including skeletal muscle, heart muscle and red blood cells. Interpretation of the enzyme is similar to ALT, while recognizing that it is much less liver-specific. Normal level in dogs is 15-66.

Alkaline phosphatase is also present in the liver, as well as bone, placenta and other locations. From the liver, it normally moves into the intestinal tract along with bile through the bile ducts. However, if bile flow is obstructed, levels within the liver may rise sufficiently to ‘back up” into the bloodstream. Patients with rapidly growing bones, puppies and kittens, as well as pregnant animals, may have elevated alkaline phosphatase levels.

Bile ducts may become obstructed at the microscopic level, inside the liver, or the macroscopic level, in the large ducts that leave the gall bladder, pass through the pancreas and enter the intestinal tract, where bile aids in the digestion of fats.

GGTP or gamma glutamyl transpeptidase, also becomes elevated in biliary obstruction, and is much more specific than alkaline phosphatase. It is also a much newer test.

It is important to realize that these are not measurements of liver function, rather they are measurements of liver damage. Now, that won’t keep physicians or veterinarians from calling them liver function tests. It’s not that we don’t know better, it’s just the term used as an inappropriate shortcut. To assess the function of the liver, we will discuss bile acids in this series.

See you tomorrow, Dr. Randolph.

24 Comments

  1. I have a 10 year old Bichpoo. Two years ago my vet stated my dogs Alkaline Phosphatase level was high. When we went back for her 6 month appointment the levels were even higher. She gave me a script for Denamarin to be given on an empty stomach. My dogs have never been good at taking medication unless it it wrapped up in something very tasty. If I attempt to just pop the pill into her throat and massage it down she will throw it up about a half hour later. The vet said I could use a small amount of food to get her to take the pill. Six months after that her levels were still high around 800. My vet suggested an ultrasound which I scheduled. The ultrasound did not reveal anything but possibly a bout of pancreatitis in the past. Her urine sample was good. My dog is eating fine and drinking about the same (she never drank a lot of water). While she isn’t overly active at home, I can take her on a 2 mile walk with no problem. Unfortunately, I myself had a few surgeries earlier this year and could not always get out to get something I could put the pill into to get her to take it on a regular basis. In April I took her in for her semiannual checkup. Her Alkaline Phosphatase was up to 1490 and another liver enzyme was also elevated. My vet wanted me to make sure my dog had her Denamarin daily for the next 3 weeks and then retest her blood. I just had a call from the vet stating the Alkaline Phosphatase was at 1384 and the other liver enzyme was back in the normal range (high end). Her thoughts were that since I cannot get my dog to take Denamarin on an empty stomach that she is not getting the full benefit of the drug. She wants me to continue with the Denamarin but to also give my dog something called Ursodiol at night. Just wondering what your thoughts are on taking these two medications. Also my dog needs some dental work done, her breath is bad. Do the enzymes need to be back to normal before I consider having her have anesthesia?

    • I’d like to see your veterinarian refer you to a board-certified internist to get to the bottom of this. Please write back with that specialist’s report. Thanks for reading, Dr. Randolph.

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