- the most common cause of persistent hypoglycemia in early infancy.
- may be macrosomic (anabolic effects of ~ in utero)
- onset is from birth to 18 mo,depending on severity
- when less severe, hypoglycemia may appear after the first few weeks to mos, when feeding is less frequent i.e esp overnight, and hyperinsulinemia prevents mobilization of endogenous glucose
- steroids or diazoxide (a HTN med) can increase blood glucose levels.
Common presenting features
- increasing appetite/demand for feeds
- wilting spells
- frank seizures
- rapid development of fasting hypoglycemia after 4-8 hours (vs other cause of hypoglycemia, ie in nonhyperinsulemic causes, it takes on average 18 hours fasting to reach hypoglycemia, vs 2.1 hrous.
- need for high rates of glucoes infusion, often > 10-15 mg/kg/min
- absence of ketonemia or acidosis
- elevated c-peptide or proinsulin levels at time of hypoglycemia.
- there will usually be a good response to glucagon (increase by 40 mg/dL glucose) implying that although insulin restrains glucose mobilization, glycogenolytic mechs are still intact.
- IGF BP-1. Secretion is acutely inhibited by insulin; concentrations are low during hyperinsulinism induced hypoglycemia. In normal hypoglycemic patients (ie fasting) IGF BP-1 levels should be higher, because insulin levels should be low.
- once endogenous hyperinsulinism has been established through measurements taken at the time of spontaneous or fasting hypoglycemia, the ddx includes:
Congenital hyperinsulinism (or persistent hyperinsulinemic hypoglycemia of infancy (PPHI), formerly called nesidioblastosis) can be broken down into three entities
Leucine-sensitive hypoglycemia is a from of the
hyperinsulinemia-hyperammonemia syndrome. Leucine is a potent amino acid for
stimulating insulin secretion.
r/o Munchausen syndrome by proxy
After the first 12 mo of life, hyperinsulinemic states are uncommmon until islet cell adenomas appear. Consider this dx in any child older than 5 years presenting with hypoglycemia. Consider MEN Type I (multiple endocrine adenomatosis) Wermer syndrome
Rare association with hypoglycemia: antibodies to insulin or the insulin