Why Protein Causes Low Blood Sugar in Children | HI/HA

If your child’s low blood sugar is triggered by eating protein-rich foods, it usually indicates a specific subtype of Congenital Hyperinsulinism (CHI) known as Hyperinsulinism-Hyperammonemia (HI/HA) syndrome ^[1].

While CHI is generally thought of as a condition where blood sugar drops during fasting, HI/HA is different. It is caused by a mutation in the GLUD1 gene, which provides instructions for making an enzyme in the pancreas called glutamate dehydrogenase (GDH) ^[2]. To understand why protein causes blood sugar to drop, it helps to look at how this enzyme normally works and how the mutation changes things.

How Protein Triggers Low Blood Sugar

In a person without CHI, eating protein introduces an amino acid called leucine into the bloodstream. Leucine signals the GDH enzyme in the pancreas to release a small, controlled amount of insulin to help the body process the meal ^[2].

In children with HI/HA syndrome, the mutated GLUD1 gene causes the GDH enzyme to be overactive, essentially removing its normal “brakes” ^[2]. When a child with this mutation eats protein, the leucine over-stimulates the already hyperactive GDH enzyme. This tricks the pancreas into releasing a disproportionately large, inappropriate surge of insulin ^[2].

Because insulin’s job is to move sugar out of the blood and into cells, this sudden flood of insulin causes blood sugar levels to crash rapidly ^[1]. This is often called protein-induced or postprandial (after-meal) hypoglycemia, and it typically occurs within a couple of hours after eating a protein-heavy meal.

Managing Protein Sensitivity

If your child has GLUD1 hyperinsulinism, their dietary and medical management will look different from other forms of CHI.

Excellent Response to Diazoxide

The most encouraging news for families dealing with HI/HA syndrome is that this subtype generally responds exceptionally well to diazoxide, an oral medication ^[1][2]. Diazoxide works by keeping the potassium channels in the insulin-producing cells open, which prevents the inappropriate release of insulin even when the child eats protein ^[2]. For most children with GLUD1 mutations, diazoxide successfully stabilizes blood sugars.

While diazoxide is highly effective, it does have common side effects that you should expect and discuss with your medical team. These include fluid retention (swelling) and hypertrichosis (excessive body hair growth), which can be distressing if you are not prepared for it but are manageable under medical supervision ^[2].

Dietary Adjustments

Because protein is essential for your child’s growth and development, doctors do not recommend eliminating it. Instead, if medication alone isn’t keeping blood sugars perfectly stable, a metabolic dietitian may recommend:

• Spreading protein out: Giving smaller amounts of protein throughout the day rather than a large portion at one meal helps avoid a sudden, large dose of leucine ^[1]. You generally do not need to strictly count leucine, just portion the overall protein reasonably.
• Pairing foods: Serving carbohydrates alongside protein to help counteract the insulin surge. For example, rather than eating plain nuts, your child might eat an apple with a small handful of almonds.

Beyond Blood Sugar: Other Features of HI/HA

It is important to know that the GLUD1 mutation affects more than just insulin. The syndrome gets its full name from two other key features:

• Elevated Ammonia (Hyperammonemia): The same overactive enzyme causes the liver to produce slightly more ammonia than normal, leading to mild hyperammonemia (elevated ammonia in the blood) ^[1][2]. Unlike other metabolic disorders, the ammonia levels in HI/HA do not typically reach dangerous levels ^[1]. This means it rarely requires specific ammonia-scavenging drugs or intense monitoring for liver toxicity, which is often a huge relief for parents.
• Neurological Health: The GLUD1 gene is also active in the brain. Some individuals with HI/HA syndrome may experience neurological challenges, such as learning disabilities, ADHD, or a specific type of seizure called an atypical absence seizure (where a person briefly stares blankly or loses awareness) ^[2]. These challenges can occur independently of blood sugar control ^[2].

Because of these unique features, a child with protein-induced hypoglycemia should be closely monitored by both a pediatric endocrinologist for their blood sugar and a neurologist to support their brain development.