The HADH gene gives your cells instructions for an enzyme that helps break down fat for energy, especially when you have not eaten for a while. This gene helps your body keep energy and blood sugar steadier between meals. If the gene is not working properly, some people develop repeated low blood sugar episodes because the body releases too much insulin and cannot use fat normally. This can lead to sweating, shakiness, unusual sleepiness, or seizures, often during fasting or illness.
What is a gene?
A gene is a section of DNA that carries instructions your cells use to make molecules or regulate activities in the body. Some genes provide the directions for producing proteins, which are the functional parts of cells. Others mainly guide when certain activities occur, where they happen, and how active they are. Together, genes affect how the body develops and works, and they can influence how you respond to food, stress, or medications. More information on this topic is available in the LearnHub.
Overview
HADHGene function
What if the gene works
The HADH gene helps cells break down certain fats to make energy, especially during fasting. It also helps support normal insulin release from the pancreas.
Risk
What if the gene does not work
When the HADH gene does not work well, the body may release too much insulin and cause low blood sugar, often from infancy. Effects can range from milder to more severe, influencing when symptoms start and how often episodes happen.
Treatment
What does that mean for your treatment
Pathogenic or loss-of-function variants in the HADH gene are usually linked to diazoxide responsive hyperinsulinism, so diazoxide is often the main drug used to reduce low blood sugar episodes. This finding can support medical treatment rather than early pancreatic surgery in many people, although response still needs close monitoring.
Conditions associated with HADH
Gene function
What if the gene works
When you go several hours without eating, your cells start using more stored fat for fuel. The HADH gene helps make that possible by supporting a key step in fat breakdown inside mitochondria, the parts of cells that produce energy. This steady work helps your body meet everyday energy needs.
Inside mitochondria, the HADH gene helps cells process certain fats step by step. Its protein changes a fat fragment into the next form so the energy-making pathway can keep moving.
By moving this pathway forward, the HADH gene supports how the body breaks down fat for energy. This gives cells another fuel source when they need steady day-to-day energy.
This activity is especially important during overnight fasting, exercise, or longer gaps between meals. It helps your body tap stored fat in a smooth, routine way.
What is a variant?
A genetic variant is a minor change in a gene’s DNA sequence. These changes are common and help explain normal differences between people, such as appearance, metabolism, or how the body reacts to environmental influences. Many variants do not have any noticeable effect and are simply part of natural genetic variation. Sometimes, though, a variant changes how a gene works to a greater degree and may contribute to, or cause, a genetic condition.
Genetic variants
What if the gene does not work
Variants in the HADH gene can change the enzyme’s shape, stability, or ability to work inside mitochondria, the cell parts that handle energy. In practical terms, how HADH gene variants affect function depends on how much activity remains. Milder variants may leave partial enzyme function, while more severe variants can lead to little or no working enzyme or disrupt its interaction with other proteins that help control insulin release. This often influences how early and how strongly low blood sugar problems appear.
How variants are linked to conditions
Pathogenic variants in the HADH gene can cause a rare inherited form of hyperinsulinemic hypoglycemia, sometimes called familial hyperinsulinism type 4. In this condition, babies or children may have episodes of low blood sugar, which can be triggered by fasting or protein rich meals. For people reading about HADH gene variants linked to conditions, this is the main well-established association. A person usually needs disease-causing variants in both copies of the gene for the diagnosis to be confirmed.
A variant is not necessarily a diagnosis
Variants in genes are a routine part of human biology and are widely found in the general population. Most do not directly affect health and instead represent normal human diversity. For many genes, carrying a variant linked with a condition suggests a possible association rather than a definite diagnosis, especially when several genes and environmental factors also play a role. In some situations, though, a single well-characterized variant in a specific gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For HADH, the main factor that changes risk is inheritance: a child is at higher risk when both parents carry a disease-causing change in the HADH gene. In people already living with HADH-related low blood sugar, long gaps without food and sometimes high-protein meals can bring on episodes. Lifestyle changes do not remove the genetic cause.
Inheritance of HADH variants
HADH-related conditions are inherited in an autosomal recessive pattern. This means a child usually needs to inherit one HADH gene variant from each parent to be affected, while parents who carry one variant are typically unaffected carriers. When both parents carry a HADH gene variant, each pregnancy has a 25% chance of an affected child, a 50% chance of a carrier child, and a 25% chance of a child who inherits neither variant. For families asking how HADH gene variants are inherited, this pattern affects sons and daughters equally.
What does my HADH result mean for my family?
For HADH, family implications usually follow a recessive pattern. Parents of an affected child are often healthy carriers, and brothers or sisters may also be affected or be carriers even if they seem well. Other close relatives may also carry the family’s HADH change, so the result can matter for future pregnancies and for relatives planning children.
Genetic information
Genetic testing
How you find out about variants
Genetic testing for variants in the HADH gene usually uses a blood sample or cheek swab. The lab reads the gene's DNA code to look for changes that may help explain repeated low blood sugar or confirm a suspected inherited condition. Results may find a relevant variant, find none, or show a variant that needs further interpretation.
When should I consider getting a genetic test?
Genetic testing for the HADH gene may be worth considering in babies or children with repeated low blood sugar, especially if testing suggests the body is making too much insulin or if similar episodes run in the family. It can help confirm an inherited cause of low blood sugar and clarify risks for relatives.
A genetic result is only one part of your health story
A genetic result can provide useful insight, but what it can tell you depends on the condition and the type of variant involved. Many factors, including lifestyle, environment, age, and medical history, influence how the body works over time. For some conditions, especially those shaped by many genes, genetic information provides context rather than certainty and is best understood together with other parts of care. In other situations, a genetic result may offer a clear answer. In areas such as medication response, genetic results can also help make sense of individual experiences.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Some people break down a drug more slowly or more quickly, while others are more or less sensitive to its effects. This helps explain why the same treatment can work well for one person but cause fewer benefits or more side effects in another. These differences are common and are one of several reasons medication response can vary from person to person.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in genes can shape the way someone responds to a medication. By studying links between genes and drugs, it helps explain why the same treatment may not work in the same way for everyone. For many medicines, genes affect both how the body handles a drug and how strong its effects are. This information can support better informed, more personalized treatment choices. More detail is available in the LearnHub.
Drugs influenced by the HADH gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medicine choices, so any concerns about side effects, new symptoms, or starting or changing treatment are best discussed with your doctor.
History
Research on the HADH gene grew out of mid 20th century work on how the body breaks down fat for energy. Initially understood only through enzyme studies, it was later recognized as tied to a specific gene on chromosome 4. From these first observations, research expanded steadily. In the early 2000s, pathogenic variants in the HADH gene were linked to a rare inherited form of low blood sugar caused by too much insulin, which gave the gene clearer clinical importance. Since then, the HADH gene has been studied mainly in metabolic medicine and genetic diagnosis rather than in public awareness campaigns.