Amy Nett: Next question from Amber. She says, “How do you approach an elevated LDH? And she says, the LDH is 308 without other signs of frank disease. I know this is an indicator of cellular death and is nonspecific. Should I repeat and follow the trend or does this warrant further work-up?”
Yes, so then she says this is also the patient with the elevated parathyroid hormone, vitamin D of 55 and normal calcium, so yes, absolutely. If you see an elevated lactate dehydrogenase, you need to order the lactate dehydrogenase isoenzymes. Because remember, lactate dehydrogenase is an enzyme and it’s found in several different tissues in the body, so remember, lactate dehydrogenase is found in the heart, the liver, skeletal muscles, brain, lungs and red blood cells. If you have seen lactate dehydrogenase from that single measurement, you don’t know which of those tissues is indicating a problem, right?
Lactate dehydrogenase has five forms, or what they call isoenzymes, and each of the isoenzymes has just a slightly different structure, so meaning the lactate hydrogenated isoenzyme that’s found in the heart has a slightly different structure than the one that’s found in the liver. Again, if you go to the LabCorp test menu, just type in lactate dehydrogenase and you should get an option to run the isoenzymes. That’s going to give you more information because if it’s lactate dehydrogenase that’s found in the heart muscles, the isoenzyme that’s found in the heart muscle, you need to think about whether or not there is a recent small myocardial infarction. If it’s isoenzyme that’s found in the liver, you need to make sure you’re running a complete hepatic function panel. Think about getting an ultrasound of the liver. The isoenzyme is going to help direct you towards which follow-up tests you need to do, where do you need to be looking. I always work up an elevated lactate dehydrogenase. I think it’s pretty important to know which tissue it’s coming from, so that’s how I approach it.