Endocrine and Metabolic Disorders
Glucose homeostasis
Screen infants at risk, including infants of diabetic mothers, LGA, SGA, preterm, and those with perinatal stress, at 1-2 hours of age. A glucose below 40 mg/dL in the first 4 hours or below 45 mg/dL thereafter needs action. If symptomatic (jitteriness, lethargy, apnea, seizures), give 10% dextrose 2 mL/kg IV and start an infusion at 4-6 mg/kg/min; if asymptomatic, feed and recheck in 30 minutes. Persistent hypoglycemia suggests hyperinsulinism and needs a critical sample.
Thyroid and adrenal disorders
Newborn screening detects congenital hypothyroidism; treat with levothyroxine 10-15 mcg/kg/day, starting by 2 weeks to protect neurodevelopment. Congenital adrenal hyperplasia from 21-hydroxylase deficiency causes salt-wasting at 1-3 weeks: hyponatremia, hyperkalemia, hypotension, and ambiguous genitalia in females. Treat with hydrocortisone, fludrocortisone, and sodium chloride; monitor 17-hydroxyprogesterone.
Metabolic disease
Unexplained acidosis, hyperammonemia, or hypoglycemia should prompt a metabolic workup, including ammonia, lactate, and amino acids. PKU and galactosemia are detected by newborn screening; galactosemia requires immediate lactose-free feeding.
Worked example
An infant of a diabetic mother is jittery at 1 hour with glucose 28 mg/dL. Reasoning: symptomatic hypoglycemia. Give 2 mL/kg D10W IV, begin infusion at 6 mg/kg/min, feed, and recheck in 30 minutes. If glucose remains low, increase infusion and evaluate for hyperinsulinism.
Traps
- Giving a dextrose bolus to every asymptomatic low glucose instead of feeding first.
- Missing CAH in a male infant with vomiting and weight loss.