Lactate Dehydrogenase (LDH): What Does It Indicate in the Body?
What is Lactate Dehydrogenase (LDH)?
Lactate dehydrogenase (LDH) is a vital enzyme found in almost all cells. When damage occurs in cells or tissues, LDH is released into the bloodstream and its level in the blood rises. Although a certain amount of LDH is naturally present in the blood, an increase is often associated with a problem at the cellular or tissue level.
By measuring LDH levels in the laboratory, important information can be obtained about whether there is tissue damage and whether this damage is progressing.
How is the LDH Test Performed and In Which Situations Is It Used?
For LDH measurement, blood is usually drawn from a vein in the arm and no special preparation is required for the test. This biochemical test, which can be performed quickly, greatly assists the physician in evaluating patients suspected of cell and tissue damage. Especially if there is suspicion of disease in organs such as the heart, liver, lungs, and muscles, the LDH test is a frequently used method.
The LDH test can also be used to monitor the patient's response to certain treatments or to assess the severity of acute/chronic tissue damage.
What is Lactate Dehydrogenase (LDH) and What Is Its Role in the Body?
LDH is basically an enzyme that plays a role in obtaining energy from glucose (sugar) taken into the body. It has various subtypes (isoenzymes) in different tissues and organs. It is especially abundant in the heart, liver, lungs, kidneys, and muscle tissues. Therefore, LDH measurement is a critical tool in investigating diseases of these organs and systems.
In total LDH measurement, the main five different LDH isoenzymes in the body are evaluated together. Since each isoenzyme is found in different proportions in various tissues, identifying which isoenzyme is elevated can provide guidance about which organ or tissue is affected.
LDH Isoenzymes and Their Locations
There are five main LDH isoenzymes. Each is predominantly found in different parts of the body:
LDH-1: Abundant in the heart and kidneys. Its elevation usually indicates damage in these organs.
LDH-2: Most concentrated in red blood cells (erythrocytes). Its elevation may indicate a problem in blood cells.
LDH-3: Predominant in lung tissue. Its increase may suggest a problem related to the lungs.
LDH-4: Found in the kidneys and lymph nodes, as well as in white blood cells. It may rise in case of damage or dysfunction in these areas.
LDH-5: Located in liver and muscle tissues. An increase in its value raises the possibility of disease in the relevant tissue and organs.
What Does High LDH Mean?
When a person's LDH level rises above reference values, the most common reason is cell or tissue damage. Some situations, such as after intense exercise or exposure to severe cold, can also cause a temporary and insignificant increase in LDH. However, in some diseases or conditions, a significant increase in LDH levels can be observed. The pattern of elevation in various subtypes (isoenzymes) of LDH provides more information about which organ or tissue may be affected.
Health Conditions That May Cause High LDH
High LDH does not always indicate disease; sometimes physiological or temporary reasons may play a role. However, the following conditions can cause a significant increase in LDH levels:
Various types of cancer (e.g., testicular, lymphoma)
Neurological diseases such as cerebral vascular occlusion or stroke
Liver, kidney, or heart diseases
Pulmonary embolism (vascular occlusion due to clot)
Muscle diseases or injuries
Pancreatitis (inflammation of the pancreas)
Blood diseases such as hemolytic and pernicious anemia
Infections (e.g., meningitis, pneumonia)
Ischemia (reduced blood flow to tissues)
Bone fractures and severe muscle trauma
Certain chronic diseases or medications used
What Does Low LDH Indicate?
It is rare for LDH levels to fall below normal limits and is generally not considered a health problem on its own. It is thought that excessive vitamin C intake or, rarely, some genetic factors may cause a decrease in LDH levels. Individuals with low LDH values may tire more quickly during high-intensity physical activities and may experience cramps or pain in the muscles. Nevertheless, these findings should not be definitively attributed to low LDH, and if there are suspicious symptoms, medical evaluation should be performed.
What Are the Normal Values of LDH in the Blood?
The level of LDH in the blood may vary according to age and gender. The generally used reference ranges are as follows:
Newborn (0-1 month): 225-600 U/L
Infant (1-12 months): 100-400 U/L
Child (1-3 years): 100-300 U/L
Child (4-18 years): 100-250 U/L
Adult female: 90-220 U/L
Adult male: 90-240 U/L
The reference ranges used by each laboratory may show slight differences. Changes in values should be evaluated together with the person's clinical condition and other test findings.
For What Purposes Is the LDH Test Performed?
The LDH test aims to determine the blood level of this enzyme, which is found in almost every tissue of the body. It is frequently used for diagnosis and follow-up in the following situations:
Investigation of the presence of cell and tissue damage
Assessment of the severity of acute or chronic diseases
Monitoring the course of certain cancers or response to treatment
Differentiation of specific damage in organs such as the heart, liver, muscles, and kidneys
Evaluation of blood diseases and certain infections
The LDH test is usually requested by a physician in conjunction with other laboratory and imaging tests based on suspicion. According to the result of the test, the detected elevation or decrease is evaluated in light of other findings, and further investigations are performed if necessary.
It is important not to neglect regular medical check-ups to maintain a healthy life. If you have unexpected findings or symptoms, do not hesitate to consult a medical professional.
Frequently Asked Questions
1. Does high LDH only indicate a serious disease?
No, high LDH can sometimes be seen in cases of intense exercise or temporary physiological conditions. However, especially in persistent and markedly high values, underlying disease should be investigated.
2. Why is the LDH test requested?
Doctors usually request the LDH test when tissue or cell damage is suspected. The LDH test can also be useful in the follow-up of cancers, evaluation of organ functions, and in some types of anemia.
3. Are LDH isoenzymes measured in detail?
When necessary, separate measurement of LDH isoenzymes can be performed to determine which organ or tissue is damaged.
4. What does it mean if LDH levels are low?
Low LDH is generally not considered clinically significant. It may rarely be detected due to excess vitamin C or hereditary reasons.
5. Which diseases are suspected with high LDH?
Blood diseases, liver and muscle diseases, certain cancers, infections, and cardiovascular diseases can cause high LDH.
6. Should the LDH test be performed on an empty stomach?
It generally does not require fasting; however, if your doctor has a specific recommendation, it should be followed.
7. What does high LDH mean in children?
High LDH in children is also generally associated with tissue or cell damage, but since normal values vary by age group, results should be evaluated by a pediatric specialist.
8. Should I be concerned if LDH rises after exercise?
A slight increase in LDH level after intense physical activity is norit is mild and usually returns to its previous level in a short time. However, the cause of prolonged elevation should be investigated.
9. Should LDH elevation be monitored in cancer patients?
Yes, LDH monitoring is important in some cancers; because its increase may reflect the course of the disease. Your doctor may request this test regularly during the treatment process.
10. Is LDH level sufficient for diagnosis on its own?
No, the LDH test only indicates that there may be a problem in the body. A comprehensive medical evaluation is required for a definitive diagnosis and treatment guidance.
11. My LDH result is high, what should I do?
If your result is above the expected range, you should consult your doctor without panicking. Your doctor will investigate the cause of the situation by requesting additional tests.
References
World Health Organization (WHO) – Laboratory testing for health care
Centers for Disease Control and Prevention (CDC) – Laboratory tests
American Association for Clinical Chemistry (AACC) – LDH Test Information
Kumar, V. et al. “Robbins and Cotran Pathologic Basis of Disease.” 10th Edition, Elsevier
Mayo Clinic – LDH Test: Why it's done, results and risks