Definition, Diagnostic Criteria & Classification

Question	Answer
1. Define Congenital Adrenal Hyperplasia (CAH). What is the commonest enzyme deficiency?	CAH is a family of autosomal recessive inborn errors of adrenal steroidogenesis characterized by enzymatic blocks in cortisol biosynthesis. Deficiency: 21-Hydroxylase Deficiency (21-OHD), caused by mutations or gene conversions in the CYP21A2 gene on chromosome 6p21.3, accounts for $> 90-95\%$ of all CAH cases.
2. Classify 21-Hydroxylase Deficiency into its clinical subtypes.	1) Classic Salt-Wasting (SW) CAH (75% of classic): Complete enzyme deficiency ($<1\%$ activity). Aldosterone and cortisol deficiency cause fatal salt-wasting crisis (shock, hyponatremia, hyperkalemia) at 7–21 days of life, accompanied by severe prenatal virilization in 46,XX females. 2) Classic Simple Virilizing (SV) CAH (25% of classic): Moderate enzyme deficiency ($1-2\%$ activity). Sufficient aldosterone to prevent neonatal salt crisis; presents with prenatal virilization of external genitalia in 46,XX females, and pseudoprecocious puberty in boys. 3) Non-Classic (Late-Onset) CAH: Mild enzyme deficiency ($20-50\%$ activity). Normal genitalia at birth; presents in adolescence with hirsutism, severe acne, oligomenorrhea, and PCOS-like phenotype.
3. Detail the Prader Staging of external genital virilization in 46,XX females.	- Stage 0: Normal female external genitalia. - Stage I: Mild clitoromegaly without labial fusion. - Stage II: Clitoromegaly with posterior labial fusion and separate urethral and vaginal orifices. - Stage III: Greater clitoromegaly, extensive labial fusion, single common urogenital sinus orifice at base of phallus. - Stage IV: Phallic enlargement with hooded prepuce, complete fusion of labioscrotal folds, urogenital opening on the phallic shaft (hypospadias-like). - Stage V: Completely virilized male-appearing external genitalia with a penile urethra at the tip of the glans (empty scrotum without palpable testes).
4. What are the diagnostic endocrine laboratory cutoffs for 21-OHD CAH?	- Serum 17-Hydroxyprogesterone (17-OHP): The cardinal diagnostic biomarker. - Normal newborn: $<2\text{ ng/mL}$ ($<200\text{ ng/dL}$). - Classic CAH Diagnostic: Baseline morning 17-OHP $> 10\text{ ng/mL}$ ($> 1000\text{ ng/dL}$), frequently exceeding $50-100\text{ ng/mL}$ ($5000-10000\text{ ng/dL}$). - Elevated: Plasma ACTH, Plasma Renin Activity (PRA), Androstenedione, and Testosterone. - Low / Inappropriately Normal: Serum Cortisol and Aldosterone.
5. VIVA TRAP: Why does CAH present a gender paradox in diagnosis and timing of mortality?	- 46,XX Females: Recognized at birth due to ambiguous external genitalia (Prader I-V), prompting early endocrine workup before salt-wasting crisis occurs. - 46,XY Males: Have normal male external genitalia (or subtle scrotal hyperpigmentation/mild penile enlargement). They appear healthy at birth, are discharged unnoticed, and present catastrophically in adrenal collapse/shock at Day 7 to 21 of life with vomiting (often misdiagnosed as pyloric stenosis or septic shock) and have a high rate of unrecognized neonatal mortality!

Pathophysiology & Complications

Question	Answer
6. Explain the biochemical shunting pathway in 21-Hydroxylase Deficiency.	21-Hydroxylase converts Progesterone to 11-Deoxycorticosterone (mineralocorticoid pathway) and 17-OHP to 11-Deoxycortisol (glucocorticoid pathway). When 21-hydroxylase is blocked: 1) Cortisol deficiency removes negative feedback on the anterior pituitary $\rightarrow$ Massive ACTH hypersecretion. 2) High ACTH hyperstimulates the adrenal cortex, causing adrenal cortical hyperplasia. 3) Upstream steroid precursors (Progesterone and 17-OHP) accumulate enormously and are shunted directly into the intact adrenal androgen pathway via 17,20-lyase $\rightarrow$ Massive overproduction of DHEA, Androstenedione, Testosterone, and DHT, producing profound fetal virilization.
7. VIVA TRAP: How do you clinically and biochemically differentiate an Adrenal Crisis in CAH from Congenital Hypertrophic Pyloric Stenosis (CHPS)?	Both present in a 2- to 4-week-old infant with forceful projectile vomiting, dehydration, and failure to thrive:
Feature	Congenital Adrenal Hyperplasia
:---	:---
Serum Sodium	Hyponatremia (< 125 mEq/L)
Serum Potassium	Hyperkalemia (> 6.5 mEq/L)
Acid-Base Status	Metabolic Acidosis
External Genitalia	Ambiguous in 46,XX / Hyperpigmented
Abdominal Exam	Soft, no mass
8. What are the life-threatening ECG changes of hyperkalemia in an adrenal crisis?	1) $K^+ > 6.5\text{ mEq/L}$: Tall, peaked, symmetrical, narrow-base "tented" T waves. 2) $K^+ > 7.0-7.5\text{ mEq/L}$: Prolongation of PR interval, flattening and loss of P waves. 3) $K^+ > 8.0\text{ mEq/L}$: Widening of QRS complex, blending with T wave into a sine-wave pattern, culminating in ventricular tachycardia, ventricular fibrillation, and asystole.
9. What is Testicular Adrenal Rest Tumor (TART)?	Benign, ACTH-dependent ectopic adrenal cortical tissue rests trapped within the rete testis in boys with CAH. Driven by poor disease control and chronically elevated ACTH. Manifests as bilateral, lobulated, painless intratesticular masses that compress seminiferous tubules, causing irreversible azoospermia and infertility. Screened via annual testicular ultrasound starting at 8–10 years.

Guidelines & Management Protocols (Endocrine Society Guidelines)

Question	Answer
10. Detail the Emergency Resuscitation Protocol for an Acute Adrenal Crisis.	1) Airway & Breathing: High-flow oxygen. 2) Vascular Access: Two large-bore IV cannulae or intraosseous needle. 3) Fluid Resuscitation (Volume Expansion): - 0.9% Isotonic Normal Saline at $20\text{ mL/kg}$ IV bolus over 20–30 minutes. - Strict Contraindication: NEVER give potassium-containing fluids (no Ringer's Lactate). 4) Hypoglycemia Correction: 10% Dextrose $2\text{ to } 5\text{ mL/kg}$ IV push stat. 5) Emergency Glucocorticoid Replacement: - Hydrocortisone Sodium Succinate: Stat IV bolus of $25\text{ mg}$ (infants $<1$y), $50\text{ mg}$ (children $1-5$y), or $100\text{ mg}$ (older children), followed by $50\text{ to } 100\text{ mg/m}^2/\text{day}$ divided Q6H IV. 6) Emergency Hyperkalemia Membrane Stabilization: If ECG changes or $K^+ > 7.0\text{ mEq/L}$, administer 10% Calcium Gluconate $0.5\text{ mL/kg}$ IV over 5–10 minutes under continuous cardiac monitoring.
11. What is the standard Long-Term Maintenance Regimen for Classic CAH?	1) Glucocorticoid Replacement (Oral Hydrocortisone): - Dose: $10\text{ to } 15\text{ mg/m}^2/\text{day}$ orally divided into 3 doses daily (TID). Short half-life mimics diurnal physiology. 2) Mineralocorticoid Replacement (Oral Fludrocortisone): - Dose: $0.05\text{ to } 0.2\text{ mg/day}$ (typically $0.1\text{ mg}$ once daily). Normalizes blood pressure and suppresses Plasma Renin Activity (PRA). 3) Sodium Chloride ($NaCl$) Supplementation in Infancy: - Dose: $1\text{ to } 2\text{ grams/day}$ ($17-34\text{ mEq/day}$) table salt added to daily milk feeds until 1 year of age (infant kidney has aldosterone resistance and breast milk is naturally low in sodium).
12. VIVA TRAP: What is the target level for 17-OHP during maintenance therapy? Should it be normalized?	NEVER normalize 17-OHP into the normal reference range ($<100\text{ ng/dL}$)! To completely suppress 17-OHP into the normal range requires supraphysiological glucocorticoid doses that cause severe growth failure, iatrogenic Cushing syndrome, and permanent adult short stature. Target Monitoring Range: Early morning pre-dose 17-OHP should be maintained between $400\text{ and } 1000\text{ ng/dL}$ ($12-30\text{ nmol/L}$) along with normal age-specific androstenedione and testosterone.
13. Detail the "Sick Day Rules" for families of a child with CAH.	1) Mild Febrile Illness / Minor Surgery: Double or Triple the oral hydrocortisone dose ($30-45\text{ mg/m}^2/\text{day}$) until fever resolves (usually 48–72 hours). Fludrocortisone dose remains unchanged. 2) Vomiting, Diarrhea, Inability to Retain Oral Meds, or Major Trauma: Immediately inject Intramuscular (IM) Hydrocortisone (Solu-Cortef) at home ($25\text{ mg}$ for $<1$y, $50\text{ mg}$ for $1-5$y, $100\text{ mg}$ for $>5$y) and rush to emergency room. 3) Emergency ID: Child must wear an emergency medical alert bracelet stating "Adrenal Insufficiency".

VIVA TRAPs & Counter-Questions

Question

Answer

14. VIVA TRAP: A newborn has ambiguous genitalia with Prader IV virilization, but on palpation, a gonad is palpable in the right inguinal fold. Is this Classic 21-OHD CAH?

ALMOST CERTAINLY NOT.
In Classic 21-OHD CAH in a 46,XX female, the internal gonads are normal intra-abdominal ovaries; ovaries NEVER descend into the inguinal canal or labioscrotal folds.
The Golden Rule of DSD: If a gonad is palpable in an infant with ambiguous genitalia, it contains testicular tissue! The diagnosis is 46,XY DSD (e.g., partial androgen insensitivity, 5-alpha-reductase deficiency) or Ovotesticular DSD, NOT 21-OHD CAH!

15. Counter-Question Chain: "A mother with a previous child with classic 21-OHD CAH becomes pregnant again. Can prenatal virilization of a female fetus be prevented?"

1) Yes: Prenatal Dexamethasone Protocol.
2) Mechanism: Dexamethasone crosses the placenta un-inactivated by placental 11$\beta$-HSD2 and suppresses the fetal pituitary ACTH, halting adrenal androgen synthesis and preventing clitoromegaly and labial fusion.
3) Timing: Must start before 7 to 9 weeks of gestation (before genital virilization begins).
4) Genetic Triage: Non-invasive prenatal diagnosis (NIPD) via maternal cell-free fetal DNA (cfDNA) at 6–8 weeks to determine fetal sex and CYP21A2 status.
5) Discontinuation: If the fetus is male (46,XY) or an unaffected female, dexamethasone is immediately stopped; continued until term only if the fetus is confirmed to be an affected 46,XX female.