Which of the following is the most common cause of neonatal hypoglycemia in preterm infants?

Explanation

## Neonatal Hypoglycemia in Preterm Infants ### Pathophysiology of Preterm Hypoglycemia **Key Point:** Preterm infants have immature hepatic enzyme systems and depleted glycogen stores, making them highly susceptible to hypoglycemia within the first 24–48 hours of life. Preterm infants (<34 weeks) have: - Reduced hepatic glycogen content (only 1–2% of liver weight vs. 5% in term infants) - Immature gluconeogenic enzymes (glucose-6-phosphatase, phosphoenolpyruvate carboxykinase) - Limited capacity for ketogenesis and fatty acid oxidation - High metabolic demands relative to energy stores ### Why Inadequate Hepatic Glycogen Stores Is Correct This is the **primary mechanism** in preterm infants. Glycogen deposition accelerates in the third trimester; preterm birth interrupts this process, leaving infants with critically low reserves. Hypoglycemia typically develops within 1–3 hours of birth if feeds are delayed. ### Differential Causes of Neonatal Hypoglycemia | Cause | Timing | Population | Key Feature | |-------|--------|------------|-------------| | **Inadequate glycogen stores** | 1–3 hrs, first 24–48 hrs | Preterm, SGA, cold stress | Most common in preterm | | **Persistent hyperinsulinemia** | Delayed (hours–days) | IDM, macrosomia, Beckwith–Wiedemann | High insulin suppresses hepatic output | | **CAH (21-hydroxylase deficiency)** | 3–7 days | Both sexes, salt-wasting variant | Cortisol deficiency impairs gluconeogenesis | | **Fatty acid oxidation defects** | Prolonged fasting | Rare genetic disorders | Presents later, with hypoketotic hypoglycemia | **High-Yield:** Preterm infants require early, frequent feeds (every 2–3 hours) and close glucose monitoring (heel-stick or continuous monitoring) in the first 48 hours to prevent symptomatic hypoglycemia. **Clinical Pearl:** Cold stress, sepsis, and respiratory distress syndrome increase glucose consumption and worsen hypoglycemia in preterm infants; maintaining normothermia and treating underlying illness are critical adjuncts to feeding. [cite:Nelson Textbook of Pediatrics 21e Ch 94]