It is important that a correct diagnosis is made for the cause of hypoglycaemia (low blood sugars). Children who require a lot of sugar solutions to keep their sugars stable may have Congenital Hyperinsulinism (CHI). In normal children, low blood sugars will switch off the sugar lowering hormone insulin, which is made in the pancreas. In CHI, insulin is made constantly, whatever the level of blood sugar. As a result, children with CHI have severe and unpredictable hypoglycaemia.
To diagnose CHI, the doctors looking after your child will measure insulin levels at the time of hypoglycaemia. They will also look at fat breakdown products, called ketones, in the blood. In CHI, ketone production is suppressed.
Once the diagnosis of CHI is made and the child’s sugars are stabilised with treatment, a blood sample for genetic testing can be sent off. Genes are “codes” like a blueprint of instructions that are present in our DNA. Several genes are important in CHI. The most important genes are called ABCC8 and KCNJ11. These genetic codes make a certain “potassium channel” that keeps the cell in the pancreas in a resting condition in normal children. In the healthy state, the pancreatic cell makes proportionate amounts of insulin to the level of sugar. In CHI, the pancreatic cell is agitated and makes too much insulin, regardless of the low blood sugars. CHI genetic testing looks for problems with these genes and a few other genes. If there is a significant change in genes, they are called mutations.
Your doctor will talk to you about genetic mutations, if they are found. It is important to understand if a genetic mutation is inherited from the father or the mother. If inherited from the father only, there is a good chance that your child may have a localised form of CHI, called focal CHI. If not, your child is likely to have the more extensive form of CHI, called diffuse CHI.