Aldosterone and Renin Levels
Aldosterone and Renin Levels in Pediatric Patients
Aldosterone and renin are crucial components of the renin-angiotensin-aldosterone system (RAAS), essential for fluid and electrolyte homeostasis in pediatric patients.
Key Points:
- Critical for blood pressure regulation
- Essential for potassium homeostasis
- Age-dependent reference ranges
- Affected by posture and salt intake
- Important in evaluation of hypertension
Renin:
- Production:
- Synthesized by juxtaglomerular cells
- Released in response to:
- Decreased renal perfusion
- Decreased sodium delivery
- Sympathetic stimulation
- Actions:
- Converts angiotensinogen to angiotensin I
- Initiates RAAS cascade
- Influences blood pressure regulation
Aldosterone:
- Production:
- Synthesized in adrenal zona glomerulosa
- Stimulated by:
- Angiotensin II
- High potassium levels
- ACTH (minor role)
- Actions:
- Increases sodium reabsorption
- Promotes potassium excretion
- Maintains fluid volume
Sample Collection:
- Timing Requirements:
- Early morning collection (8-10 AM)
- Patient should be upright for 2 hours
- Consider salt status
- Specimen Handling:
- Plasma renin: EDTA tube, ice-chilled
- Aldosterone: Serum separator tube
- Process within 30 minutes
- Protect from light
Patient Preparation:
- Dietary Considerations:
- Normal salt intake for 3 days
- Avoid licorice products
- Document sodium intake
- Medication Adjustments:
- Hold diuretics if possible
- Discontinue ACE inhibitors/ARBs
- Note beta-blocker usage
Indications for Testing:
- Primary Indications:
- Hypertension evaluation
- Electrolyte disorders
- Fluid balance abnormalities
- Growth abnormalities
- Specific Conditions:
- Primary aldosteronism
- CAH (21-hydroxylase deficiency)
- Bartter syndrome
- Gitelman syndrome
- Pseudohypoaldosteronism
Reference Ranges:
Plasma Renin Activity (Upright):
- Newborns: 2.35-37.0 ng/mL/hr
- Infants 1-12 months: 2.35-37.0 ng/mL/hr
- Children 1-10 years: 1.71-11.2 ng/mL/hr
- Adolescents: 0.5-5.9 ng/mL/hr
Plasma Aldosterone (Upright):
- Newborns: 5-175 ng/dL
- Infants: 5-90 ng/dL
- Children: 3-35 ng/dL
- Adolescents: 3-30 ng/dL
Pattern Analysis:
- Primary Hyperaldosteronism:
- High aldosterone (>15 ng/dL)
- Suppressed renin
- ARR >30 (ng/dL)/(ng/mL/hr)
- Secondary Hyperaldosteronism:
- High aldosterone
- High renin
- Normal/low ARR
- Hypoaldosteronism:
- Low aldosterone
- High renin (primary)
- Low/normal renin (secondary)
Common Disorders:
- Primary Aldosteronism:
- Adenoma
- Bilateral hyperplasia
- Familial forms
- Salt-Wasting Disorders:
- CAH
- Addison's disease
- Tubular disorders
Confirmatory Testing:
- Salt Loading Test:
- Oral or IV protocols
- Age-specific interpretations
- Contraindications
- Captopril Challenge:
- Protocol modifications for children
- Safety considerations
- Result interpretation
Special Populations:
- Neonates:
- Higher baseline values
- Salt-losing tendencies
- Rapid changes in early life
- Adolescents:
- Impact of puberty
- Exercise effects
- Dietary influences
