Congenital Hypothyroidism

Presentation

• Often asymptomatic at birth due to maternal thyroxine crossing placenta
• Detected via mandatory State Newborn Screening (high TSH, low T4)
• Clinical signs (if delayed): Prolonged physiologic jaundice, large fontanelles, macroglossia (large tongue), umbilical hernia
• Hypotonia, sluggish reflexes, feeding difficulties, constipation

Diagnosis

• Immediate confirmatory venous sample: Total T4/Free T4 and TSH
• Do not delay treatment while waiting for thyroid scans (ultrasound/radionuclide uptake)

Management

• Initiate Levothyroxine (L-T4) urgently: 10-15 mcg/kg/day as a single daily dose
• Crush pill and mix in a small amount of breastmilk/formula (never soy formula - impairs absorption)
• Goal: Normalize T4 within 2 weeks and TSH within 1 month to prevent severe irreversible intellectual disability
• Frequent lab monitoring (q1-2 months for the first 6 months)

Endocrine & Metabolic Stability

• Dextrose gel (40%): Massage 200 mg/kg (0.5 mL/kg) thoroughly into buccal mucosa for initial asymptomatic hypoglycemia.
• D10W Bolus: Exactly 2 mL/kg (yields 200 mg/kg of glucose) over 1-3 minutes if symptomatic.
• Glucose infusion rate (GIR) calculation: GIR (mg/kg/min) = (IV Rate [mL/hr] × Dextrose %) / (Weight [kg] × 6).
• Monitor for rebound hypoglycemia 30-60 minutes after discontinuing or weaning IV dextrose.
• Hold oral feeds if respiratory rate > 70 to prevent aspiration while hypoglycemic.

Standardized Discharge & Follow-Up Criteria

• Adequate weight gain explicitly > 15-30g/day over a continuous 3-5 day period.
• Maintenance of temperature in an open crib with standard clothing for 48 hours.
• Successful completion of the 90-120 minute Infant Car Seat Challenge.
• Caregiver successfully completed CPR training, rooming-in, and independent medication administration.
• Referrals placed for High-Risk Infant Follow-Up Clinic, Early Intervention (PT/OT), and appropriate sub-specialists.

Diagnostic & Management Algorithm

• Congenital Hypothyroidism Management: [START] Positive Newborn Screen -> [ACTION] Draw Stat Venous Free T4 and TSH -> [DECISION] Is Free T4 low and TSH > 40 mIU/L? -> [YES] Initiate Levothyroxine 10-15 mcg/kg/day PO immediately -> [GOAL] Normalize T4 within 2 weeks and TSH within 4 weeks to prevent irreversible mental retardation

References

1. Léger J, Olivieri A, Donaldson M, et al. European Society for Paediatric Endocrinology consensus guidelines on screening, diagnosis, and management of congenital hypothyroidism. J Clin Endocrinol Metab.