Chemistry, toxicology & urinalysis
Organ specific
Cardiac
lactate dehydrogenase
Author: Larry Bernstein, M.D.
Last author update: 1 December 2010
Last staff update: 27 June 2020
Copyright: 2002-2025, PathologyOutlines.com, Inc.
PubMed Search: Lactate dehydrogenase [title]
Table of Contents
Definition / general | Pathophysiology | Diagrams / tables | Laboratory | Additional referencesCite this page: Bernstein L. lactate dehydrogenase. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/chemistrycardiaclactatedehydrogenase.html. Accessed January 15th, 2025.
Definition / general
- LDH measures the amount of serum lactate dehydrogenase (LDH), which is released into the circulation after tissue damage
- Causes of tissue damage include acute myocardial infarction (AMI), hepatitis and acute renal failure
- LDH is elevated on the second day after AMI, and remains elevated for up to 4 days
- LD1 is usually measured
Pathophysiology
- LDH is an enzyme (EC 1.1.1.27) ubiquitous in tissue (Wikipedia - Lactate dehydrogenase)
- It has five isoenzymes, each with a different composition of M-type and H-type subunits in a tetrameric structure
- The M-type isoenzyme is predominant in liver and skeletal muscle
- The H-type isoenzyme is predominant in heart and renal cortex
- LDH catalyzes the conversion of pyruvate to lactate in the glycolytic pathway
Diagrams / tables
Images hosted on other servers:
Pyruvate to Lactate conversion
Laboratory
Methodology
Indications
Limitations
Reference ranges
- The measurement of the enzyme uses the reduction of the coenzyme NAD to NADH with increasing optical density and oxidation of lactic acid to pyruvate
- Alternatively, one can follow the reverse reaction of pyruvate to lactate and NADH to NAD at 340 nm
Indications
- Patients presenting 12+ hours after the onset of chest pain
- High levels are suggestive of acute myocardial infarction
- Staging (S classification) patients with nonseminomatous testicular cancer
- Evaluating patients with metastatic cancer
- Assessing nature of pleural / pericardial fluids: ratio of fluid LDH to upper limit of normal serum LDH of more than 0.6 suggests an inflammatory process (exudate)
Limitations
- Elevated in hemolyzed specimens, since enzyme is present in erythrocytes
Reference ranges
- A typical range is 105 - 333 IU/L
- Must interpret values in context of patient clinical findings
