What is the role of lab testing in the diagnosis of pediatric hypoglycemia?

Updated: Feb 19, 2018
  • Author: Robert P Hoffman, MD; Chief Editor: Sasigarn A Bowden, MD  more...
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Answer

Some authors have suggested measuring free carnitine, total carnitine, and acyl carnitine levels before performing a fasting study in order to detect medium-chain acyl-CoA dehydrogenase deficiency; this may prevent life-threatening hypoglycemia and hyperammonemia during the fast. Many states now conduct neonatal screening for medium-chain acyl-CoA dehydrogenase deficiency.

Measuring IGFBP-1 before and after the fast may also be useful. IGFBP-1 levels are suppressed by insulin and, therefore, increase during fasting in healthy individuals but decrease or remain stable in individuals who are hyperinsulinemic.

A glucagon stimulation test at the end of the fast may be useful as well. In most individuals, the glucose level does not increase following hypoglycemia because the glycogen stores are significantly depleted before hypoglycemia develops. However, in hyperinsulinemia, endogenous glucagon secretion and glycogenolysis are suppressed, and the plasma glucose concentration increases more than 1.9 mmol/L (35 mg/dL) following glucagon administration. Glucagon does not increase the blood glucose concentration in patients with glycogen-storage disease type I even in the fed state. Cortisol and growth hormone levels can also be drawn 30 and 60 minutes into the test to determine if levels rise following hypoglycemia.

After the fast is completed and the patient has been fed, glucose and lactate levels should be measured for evidence of glycogen synthase deficiency.

Measuring sulfonylurea, ethanol, or salicylate levels is appropriate if hypoglycemia is believed to be secondary to their ingestion. The presence of a low C-peptide level with a high insulin level suggests exogenous insulin administration.

Oral glucose tolerance tests do not aid in the diagnosis of hypoglycemia, because many healthy patients have low plasma glucose concentrations following a large glucose bolus. In addition, a low plasma glucose concentration during an oral glucose tolerance test does not prove that the patient is hypoglycemic when symptoms occur.

Commercially available genetic analysis is now available to identify many of the genetic disorders associated with hyperinsulinism.


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