The LDHA gene helps make an enzyme that lets muscles and red blood cells turn sugar into quick energy, especially during hard exercise. If it does not work properly, muscles may run short of usable energy and can break down after intense activity. This gene plays an important role in how your body keeps working when oxygen is low. Pathogenic variants can lead to exercise intolerance, muscle cramps, muscle pain, and sometimes dark urine from muscle breakdown.
What is a gene?
Genes are sections of DNA that carry instructions your cells use to make molecules or direct processes in the body. Some genes provide the information needed to produce proteins, the parts of cells that do the work. Others mainly help regulate when and where certain processes happen and how active they are. Together, genes affect how the body develops and works, and they can also shape how you respond to food, stress, or medications. To explore this topic more deeply, learn more in the LearnHub.
Overview
LDHAGene function
What if the gene works
The LDHA gene helps cells make energy from sugar, especially during exercise or when oxygen is low. It supports muscles and other tissues by changing a sugar breakdown product into lactate.
Risk
What if the gene does not work
Milder to more severe variants in the LDHA gene can limit energy release during hard exercise, often leading to exercise intolerance, muscle pain or cramps, and dark urine from muscle breakdown; some people also have breakdown of red blood cells.
Treatment
What does that mean for your treatment
No treatment or drug choice is currently guided by a pathogenic variant in the LDHA gene. The LDHA gene is being studied as a drug target in cancer and altered energy metabolism, but this work is still investigational.
Conditions associated with LDHA
Gene function
What if the gene works
Your cells use the LDHA gene to keep energy moving when demand rises. It is especially important in tissues that often need quick energy, such as working muscles. This helps explain how your body turns sugar into energy during hard exercise and other short bursts of effort.
The LDHA gene helps cells make energy from sugar when they need it fast. This is most useful during short, intense activity and in places where oxygen may be limited.
LDHA helps convert pyruvate, a sugar breakdown product, into lactate. This gives cells a practical way to keep energy production going during heavy demand.
One of its main roles is to refresh NAD+, a helper molecule cells need to keep breaking down sugar for energy. By restoring this helper, LDHA supports steady energy flow in active tissues.
What is a variant?
A genetic variant is a small difference in the DNA sequence within a gene. These differences are common and help account for normal human diversity, including differences in appearance, metabolism, and how the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. In some situations, however, a variant can change how a gene works more substantially and may contribute to or directly cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the LDHA gene can change the enzyme’s shape, stability, or ability to join with matching parts, which may reduce or block its activity. Some variants leave partial activity, while more severe variants can produce a shortened protein or almost no working enzyme at all. This is how LDHA gene variants affect enzyme activity, and the degree of change can influence how early or how strongly exercise related symptoms appear.
How variants are linked to conditions
Among LDHA gene variants linked to conditions, the main well-established one is LDHA deficiency, also called glycogen storage disease XI. Pathogenic variants in the LDHA gene can cause a rare inherited muscle condition marked by exercise intolerance, muscle cramps, and episodes of muscle breakdown with dark urine after strenuous activity. Some people also have persistently raised creatine kinase on blood tests, and some women may experience difficult labor.
A variant is not necessarily a diagnosis
Genetic variants are a usual part of human biology and are common across the general population. Most do not directly affect health and simply reflect natural human diversity. For many genes, carrying a variant associated with a condition indicates a possible link rather than a definite diagnosis, particularly when several genes and environmental factors are involved. In some situations, however, a single well-characterized variant in a specific gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For people with harmful changes in both copies of the LDHA gene, symptoms are often triggered by intense exercise, especially short bursts like sprinting or heavy lifting. Illness or fever can also make muscle pain or muscle breakdown more likely. Family history and whether one or both gene copies are affected also change risk.
Inheritance of LDHA variants
LDHA-related conditions are inherited in an autosomal recessive pattern. This means a person usually develops the condition only when they inherit two disease-causing variants in the LDHA gene, one from each parent. Parents who each carry one variant are typically unaffected carriers, and with each pregnancy they have a 25% chance of having an affected child, a 50% chance of having a child who is a carrier, and a 25% chance of having a child with no familial variant. In practical terms, this is how variants of the LDHA gene are inherited in families.
What does my LDHA result mean for my family?
For families affected by changes in the LDHA gene, close relatives may also be carriers or, less often, have the same condition. Brothers and sisters can have a higher chance of being affected if both parents carry a changed copy, even when the parents do not have symptoms. Family members may want to learn whether the same LDHA change runs in the family.
Genetic information
Genetic testing
How you find out about variants
To find out about LDHA variants, LDHA genetic testing uses a blood or saliva sample to read the LDHA gene and look for changes. Results can confirm a known family variant or help clarify whether symptoms such as exercise-related muscle pain fit an inherited LDHA-related condition.
When should I consider getting a genetic test?
Consider testing if you or a close relative has repeated severe muscle pain, cramps, dark urine, or episodes of muscle breakdown after intense exercise, especially with a family history of the same pattern. LDHA testing can help confirm an inherited LDHA-related muscle condition and clarify risk for relatives.
A genetic result is only one part of your health story
A genetic result can provide useful insight, but how much it reveals depends on the condition and the type of variant involved. Other factors, including lifestyle, environment, age, and medical history, also affect how the body works over time. For some conditions, especially those shaped by many genes, genetic information offers context rather than certainty and is most helpful when viewed alongside other parts of care. In other situations, a genetic result may give a clear answer. In areas like medication response, genetic results can also help put individual experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. This helps explain why the same medication may work well for one person but less well for another, or why some people are more sensitive to side effects. Differences in how the body absorbs, breaks down, transports, or responds to a drug are common and can influence how effective a treatment feels and how well it is tolerated.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in genes can affect the way a person responds to medication. It focuses on gene and drug patterns to help explain why the same treatment may work differently in different people. With many medicines, genes can influence how powerfully a drug works or how the body handles it. This information can support treatment choices that are better informed and more personalized. More detail on this topic is available in the LearnHub.
Drugs influenced by the LDHA gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in predicting how people respond to medicines, so questions about treatment, side effects, or your overall health are best discussed with your doctor.
History
Researchers began identifying lactate dehydrogenase as a human enzyme in the mid 20th century, during a period when scientists were mapping how cells handle energy. From these first observations, research expanded steadily. By the 1960s and 1970s, different lactate dehydrogenase forms were separated and linked to specific tissues, which helped place the LDHA gene within a larger enzyme family. Later, rare inherited LDHA variants were connected with exercise related symptoms such as muscle pain and episodes of muscle breakdown, giving the gene clear clinical relevance. As gene mapping and sequencing improved, LDHA became part of the broader story of how metabolism genes were studied in both inherited conditions and cancer research.