Normal Reference Ranges of Luteinizing Hormone (LH) in Children by Age
Age-specific, analyzer-specific, and reagent-specific reference ranges must be used when interpreting pediatric LH results, as applying adult ranges leads to systematic misdiagnosis. 1, 2
Critical Methodological Requirement
Modern immunochemiluminometric assays (ICMA) or immunofluorometric assays (IFMA) with sensitivity down to 0.019 IU/L must be used for pediatric LH measurement, as older radioimmunoassays cannot accurately detect the very low prepubertal levels and will produce falsely elevated readings at low concentrations. 3, 4
Age-Specific LH Reference Ranges
Infancy (0-2 years)
- Males: Transiently elevated in first months of life, then decline 3
- Females: Lower than males in infancy 3
- Levels drop significantly after the first few months 5
Prepubertal Children (2-9 years in girls, 2-11 years in boys)
- Mean LH: 0.04 ± 0.04 IU/L (measured by ICMA) 3
- Range: Below 0.2 IU/L in all children under 10 years 6
- Urinary LH: Below 0.5 IU/L until age 9 in girls; below 1.0 IU/L until age 11 in boys 5
- No statistical difference between boys and girls after infancy 3
- Pulsatile secretion is present but with very low amplitude (mean levels as low as 0.02 IU/L detectable) 4
Early Puberty (Tanner Stage 2-3)
- Range: 0.3-6.5 IU/L 4
- LH pulse frequency increases (interpulse interval decreases from 135 minutes prepubertally to 76 minutes in early puberty) 4
- LH pulse amplitude increases 11-fold compared to prepubertal values 4
Late Puberty to Adulthood
- Increase from prepuberty: 100-fold rise in females, 50-fold in males 5, 6
- Adult female levels (follicular phase): Approximately 5.8 IU/L (116-fold increase from age 7) 6
- Adult male levels: Approximately 5 IU/L 5
GnRH Stimulation Test Reference Values
Prepubertal Children (both sexes)
- Peak stimulated LH: 1.8 ± 1.3 IU/L 3
- Interpretation: Fourfold increase from baseline is normal prepubertal response 7
Pubertal Children
- Peak stimulated LH: Greater than 5 IU/L suggests maturing gonadotropin secretion 3
- Increase from prepuberty: 20-fold rise in peak stimulated values 3
Critical Pitfalls to Avoid
- Never apply adult reference ranges to children, as this misclassifies approximately 30% of normal children as abnormal (extrapolated from hemostasis data showing similar developmental patterns) 8, 1
- Do not use reference ranges from different analyzer systems, as LH assays are highly method-dependent with significant reagent-specific differences 1, 2
- Avoid older radioimmunoassays that cannot measure below 0.5-1.0 IU/L, as they miss the critical prepubertal range and diverge markedly from ICMA values at low concentrations 3
- FSH levels are much higher than LH throughout childhood (3-6 fold higher prepubertally), so do not expect parallel values 3, 5, 4
Key Physiological Principle
The dramatic 100-fold increase in LH during puberty (compared to only 6-7 fold for FSH) makes LH the most sensitive biochemical marker of pubertal onset, with the steepest rise occurring at 9-10 years in girls coinciding with rising estradiol and physical pubertal changes. 6