Test for ACTH Level
ACTH Level in Pediatric Patients
Adrenocorticotropic hormone (ACTH) is a critical anterior pituitary hormone that regulates cortisol production from the adrenal cortex. Understanding ACTH levels is essential for diagnosing various endocrine disorders in pediatric patients.
Key Points:
- Part of the hypothalamic-pituitary-adrenal (HPA) axis
- Shows distinct circadian rhythm
- Essential for stress response
- Critical for growth and development
- Regulated by negative feedback from cortisol
Normal Physiology:
- Secretion Pattern:
- Peak levels: 6-8 AM
- Lowest levels: Midnight
- Pulsatile release throughout day
- Regulatory Factors:
- CRH (primary stimulator)
- Stress (acute stimulator)
- Glucocorticoids (negative feedback)
- Inflammatory cytokines (modulators)
Age-Related Changes:
- Newborns: Higher baseline levels
- Infants: Gradual development of circadian rhythm
- Children: Established adult-like pattern by age 3
- Adolescents: Similar to adult values
Collection Protocol:
- Timing:
- Early morning (7-9 AM) preferred
- Midnight sample if Cushing's suspected
- Serial sampling may be necessary
- Sample Handling:
- Collection in chilled EDTA tubes
- Immediate processing required
- Transport on ice
- Protect from light
Pre-analytical Considerations:
- Fasting not required
- Avoid recent glucocorticoid use
- Document current medications
- Note recent stressors or illness
- Record sampling time accurately
Indications for Testing:
- Primary Applications:
- Suspected adrenal insufficiency
- Congenital adrenal hyperplasia
- Cushing's syndrome
- Growth abnormalities
- Precocious or delayed puberty
- Secondary Applications:
- Monitoring glucocorticoid therapy
- Evaluation of pituitary function
- Assessment of stress response
- Investigation of electrolyte disorders
Reference Ranges:
Morning Values (6-8 AM):
- Newborns: 10-185 pg/mL
- Infants: 8-100 pg/mL
- Children: 5-60 pg/mL
- Adolescents: 10-60 pg/mL
Elevated ACTH:
- Primary Adrenal Insufficiency:
- Typically >100 pg/mL
- Associated with low cortisol
- Consider CAH variants
- Other Causes:
- Ectopic ACTH syndrome
- Nelson's syndrome
- Stress states
- ACTH-secreting tumors
Low ACTH:
- Secondary Adrenal Insufficiency:
- Usually <5 pg/mL
- Associated with low cortisol
- Check other pituitary hormones
- Other Causes:
- Exogenous glucocorticoid therapy
- Pituitary tumors
- Cranial radiation
- Genetic defects in POMC processing
Dynamic Testing:
- CRH Stimulation Test:
- Useful for differentiating causes
- Assess HPA axis integrity
- Monitor treatment response
- Dexamethasone Suppression:
- Evaluate Cushing's syndrome
- Monitor treatment effectiveness
- Age-specific protocols required
Interfering Factors:
- Pre-analytical:
- Stress
- Exercise
- Medication effects
- Sample handling issues
- Analytical:
- Method-specific variations
- Cross-reacting substances
- Hook effect in very high values
