Hypoglycemia

Basics

Description

  • Deficiency in counterregulatory hormones (glucagon, epinephrine, cortisol, growth hormone) or excessive insulin response
  • Serum glucose <70 mg/dL

Risk Factors

  • Strict glycemic control with insulin
  • Prior hypoglycemia episodes
  • Hypoglycemia unawareness
  • Decreased counter regulation
  • <5 yr of age or elderly
  • Comorbid conditions:
    • Renal disease
    • Malnutrition
    • Coronary artery disease
    • Liver disease

Genetics

  • Congenital metabolic and endocrine disorders that decrease gluconeogenic ability (eg, hereditary fructose intolerance)
  • Congenital hyperinsulinism
  • Neonatal diabetes mellitus (often a mutation effecting an ATP-dependent potassium channel)

Etiology

  • Increased insulin levels:
    • Overdose of oral hypoglycemic agent or insulin
    • Oral antihyperglycemics (ie, α-glucosidase inhibitors, biguanides, and thiazolidinediones) do not cause hypoglycemia alone, but may enhance the risk when used with insulin or sulfonylureas
    • Insulin pump malfunction
    • Sepsis
    • Critical illness
    • Insulinoma
    • Autoimmune hypoglycemia
    • Alimentary hyperinsulinism
    • Renal failure (partially responsible for insulin metabolism)
    • Liver cirrhosis (responsible for significant insulin metabolism)
  • Insulin pumps:
    • Insulin pumps come in many varieties
    • some with devices that use continuous glucose monitoring (CGM) to communicate with the insulin pump
    • Accuracy of CGMs is imperfect and requires calibration, which may introduce errors causing hypoglycemia
    • CGM alarms are helpful but can cause false positive soundings and false negative silence
    • Occasionally, patients fail to respond to alarms which can lead to complications such as hypoglycemia
    • Pump failure may be due to mechanical failure, detachment, leakage, blockage, battery failure, or a poor infusion site
    • Failures and tight glucose parameters on devices can lead to both diabetic ketoacidosis and hypoglycemia
    • Insulin pump malfunction may require device interrogation and specialist consultation prior to restarting therapy
  • Underproduction of glucose:
    • Alcohol (inhibitory effect on glycogen storage and gluconeogenesis)
    • Salicylates
    • β-Blockers (including eye drops)
    • SSRIs
    • Some antibiotics (eg, sulfonylureas, pentamidine)
    • Adrenal insufficiency
    • Malnutrition
    • Dehydration
  • Cerebral edema
  • Extremes of age
  • Congestive heart failure
  • Counterregulatory hormone deficiency
  • Hypothyroidism or hyperthyroidism

Pregnancy Considerations

  • 3rd-trimester pregnant patients risk relative substrate deficiency–induced hypoglycemia
  • The fetus is less likely to become hypoglycemic during mother’s hypoglycemic episode secondary to active glucose transport across placenta:
    • Oral hypoglycemic use in pregnancy may lead to profound and prolonged neonatal hypoglycemia

Pediatric Considerations

Most common cause of hypoglycemia in the 1st 3 mo of life is persistent hyperinsulinemic hypoglycemia of infancy (PHHI) in mothers with diabetes

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