A 4-week-old male infant is brought to the pediatric clinic for evaluation of poor feeding and lethargy. The parents report vomiting and weight loss. Laboratory results show hyponatremia (Na+ 128 mEq/L) and hyperkalemia (K+ 6.2 mEq/L). Which assessment finding would be most indicative of congenital adrenal hyperplasia (CAH)?
1Elevated 17-hydroxyprogesterone levels✓ 정답
2Decreased cortisol levels only
3Elevated growth hormone levels
4Decreased thyroid-stimulating hormone levels
해설
Elevated 17-hydroxyprogesterone is the most specific diagnostic finding for CAH, reflecting enzyme deficiency. Other options are not indicative of CAH in this context.
Core Nursing ExplanationKey Concept Analysis: This question assesses the ability to identify the definitive diagnostic marker for a life-threatening endocrine emergency in a newborn: Congenital Adrenal Hyperplasia (CAH). The classic presentation involves a deficiency in the enzyme 21-hydroxylase, which is responsible for converting 17-hydroxyprogesterone (17-OHP) into cortisol. The infant's symptoms (poor feeding, lethargy, vomiting, weight loss) and lab findings (hyponatremia, hyperkalemia) point to an adrenal crisis due to salt-wasting CAH. The body's attempt to compensate for low cortisol increases ACTH (Adrenocorticotropic Hormone), which stimulates the adrenal glands, leading to an accumulation of precursor hormones, most notably 17-OHP.
Answer Rationale: Key Point!Elevated 17-hydroxyprogesterone (17-OHP) is the hallmark diagnostic laboratory finding for the most common form of CAH (21-hydroxylase deficiency). It is the precursor that builds up immediately before the blocked enzymatic step. Measuring 17-OHP is a specific newborn screening test for CAH. The electrolyte imbalances (Na+ 128 mEq/L [Normal: 135-145 mEq/L], K+ 6.2 mEq/L [Normal: 3.5-5.0 mEq/L]) are critical clinical signs of the salt-wasting form but are not diagnostic; they are the consequence of aldosterone deficiency.
Distractor Analysis:
Watch out for confusion! Option ② (Decreased cortisol levels only): While cortisol is low in CAH, this finding is not specific. Low cortisol can occur in other conditions like primary adrenal insufficiency (Addison's disease) or pituitary disorders. The diagnosis of CAH hinges on identifying the specific enzyme defect by measuring the elevated precursor (17-OHP).
Option ③ (Elevated growth hormone levels): Growth hormone is not directly involved in the adrenal steroid synthesis pathway. Its levels are unrelated to CAH pathophysiology.
Option ④ (Decreased thyroid-stimulating hormone levels): TSH is related to thyroid function. While endocrine disorders can co-exist, a low TSH suggests hyperthyroidism, which is not part of the CAH presentation. The electrolyte abnormalities (hyponatremia, hyperkalemia) are classic for adrenal, not thyroid, dysfunction.
Related Concepts: In salt-wasting CAH, the deficiency in aldosterone production leads to renal sodium loss (hyponatremia) and potassium retention (hyperkalemia). The resulting hypovolemia can progress to shock. Treatment involves immediate fluid resuscitation with normal saline, glucocorticoid (hydrocortisone) and mineralocorticoid (fludrocortisone) replacement, and monitoring for hypoglycemia.
Concept Summary
IV fluids (NS), IV hydrocortisone, fludrocortisone, correct electrolytes
Side-by-Side Comparison!
Condition
Primary Electrolyte Imbalance
Key Hormone/Precursor Change
Clinical Context
Congenital Adrenal Hyperplasia (Salt-wasting)
Hyponatremia, Hyperkalemia
17-OHP ↑↑↑, Cortisol ↓, Aldosterone ↓
Newborn in adrenal crisis (2-4 weeks old)
Syndrome of Inappropriate ADH (SIADH)
Hyponatremia (Dilutional), Normokalemia
ADH (Vasopressin) ↑
Head injury, pneumonia, post-op
Primary Adrenal Insufficiency (Addison's)
Hyponatremia, Hyperkalemia
Cortisol ↓, Aldosterone ↓, ACTH ↑ (primary)
Adult with fatigue, hyperpigmentation
Anatomy, Physiology & Pharmacology Points
Adrenal Cortex Layers & Hormones: Zona Glomerulosa (Aldosterone), Zona Fasciculata (Cortisol), Zona Reticularis (Androgens). 21-hydroxylase deficiency affects cortisol and aldosterone synthesis.
Negative Feedback Loop: Low cortisol → Pituitary releases more ACTH → Adrenal gland stimulation → Hyperplasia and accumulation of precursors before the enzyme block.
Drug Therapy:Hydrocortisone (glucocorticoid replacement), Fludrocortisone (mineralocorticoid replacement). Doses must be increased during stress/illness to prevent crisis.
Memory Tips
Acronym: "CAH = Crisis, Aldosterone lack, High 17-OHP."
Visualize the Block: Imagine the steroid synthesis pathway. The 21-hydroxylase enzyme is a gate. When it's blocked, traffic (17-OHP) backs up massively behind it.
Newborn + Vomiting + Bad Electrolytes (Low Na, High K) = Think CAH until proven otherwise.
High-Frequency NCLEX Topics
CAH is a classic NCLEX-RN pediatric endocrine question. You must know: 1) The classic presentation in a 2-4 week old infant, 2) The specific lab finding (17-OHP), 3) The associated electrolyte imbalances, and 4) The priority nursing interventions during an adrenal crisis (ABCs, IV fluids, steroids).
Watch Out for Question Variations!
Symptom Identification → Priority Intervention: "The nurse is caring for a 3-week-old infant with suspected CAH who is lethargic and vomiting. What is the priority nursing action?" (Answer: Establish IV access for fluid and steroid administration).
Parent Education Focus: "The nurse is teaching parents of a child with CAH. Which statement by a parent indicates understanding?" (Answer: "I will give extra hydrocortisone if my child has a fever.").
Lab Value Interpretation: The question may give you the 17-OHP value directly and ask you to interpret it.
Nursing Clinical Practice GuideClinical Scenario: You are a nurse in the Pediatric Emergency Department. A frantic mother brings in her 4-week-old son, stating he has been "too sleepy to eat," vomiting after feeds, and has lost weight since his last check-up. On assessment, the infant is lethargic, has poor skin turgor, a sunken fontanelle, weak pulses, and a heart rate of 180 bpm.
Nursing Intervention Strategy:
Immediate Assessment (ABCs): Assess airway, breathing, and circulation. This infant is in hypovolemic shock from adrenal crisis. Anticipate orders for STAT labs (electrolytes, glucose, 17-OHP, cortisol) and a point-of-care glucose check.
Priority Actions: Establish IV access immediately. Administer an IV bolus of Normal Saline (0.9% NaCl) as ordered to correct hypovolemia and hyponatremia. Prepare to administer IV hydrocortisone (stress-dose glucocorticoid).
Ongoing Monitoring: Continuous cardiorespiratory monitoring. Strict I&O (Intake and Output). Monitor vital signs, capillary refill, and neurologic status closely. Re-check electrolytes and glucose frequently.
Family Support & Education: Explain the situation calmly to the parents. Once stabilized, begin education about CAH as a chronic condition, emphasizing the life-long need for medication, signs of adrenal crisis (vomiting, lethargy, diarrhea), and the "sick-day rules" (doubling or tripling hydrocortisone dose during illness/stress).
Patient Safety and Precautions:
Never delay treatment waiting for confirmatory 17-OHP results if clinical suspicion is high. Treat the adrenal crisis empirically.
When administering IV fluids for hyponatremia, correct it slowly to avoid central pontine myelinolysis. The goal is typically an increase of no more than 8-12 mEq/L in the first 24 hours.
Monitor for hypoglycemia and treat with IV dextrose as needed.
Nursing Procedure & Medication FlowManaging an Adrenal Crisis in an Infant:
1. Call for Help & Prepare Resuscitation Area.
2. Establish IV/IO Access: Two large-bore IVs if possible.
3. Fluid Resuscitation: Administer 20 mL/kg bolus of Normal Saline. May repeat based on perfusion.
4. Administer Steroids: Give IV Hydrocortisone (Solu-Cortef). Typical stress dose: 50-100 mg/m² IV initially, then divided doses every 6 hours.
5. Correct Electrolytes: May need additional sodium chloride supplements and management of hyperkalemia (which often corrects with fluids and steroids).
6. Monitor & Titrate: Frequent VS, glucose checks, and electrolyte panels guide ongoing therapy.
A Word from Your Senior Nurse
"Newborns can't tell us what's wrong. It's up to us to be detectives, connecting subtle clues like poor feeding and weight loss to critical pathophysiology. This case of CAH is a perfect example of why understanding 'the why' behind lab values is everything. You saw hyponatremia and hyperkalemia and immediately thought 'adrenal problem.' You connected the infant's age to the timing of a salt-wasting crisis. That kind of critical thinking saves lives. On the NCLEX, they're testing if you can make those connections under pressure. In real life, you'll be the one spotting this crisis in triage and initiating the life-saving response. Study the pathways, know the key markers, and always, always think about the whole patient."