LH and FSH Testing in Pediatrics
LH and FSH Testing in Pediatrics
Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) are crucial gonadotropins that play essential roles in sexual development and reproduction. Their measurement is fundamental in evaluating disorders of puberty, gonadal function, and reproductive health in children.
Key Points
- LH and FSH are secreted in a pulsatile manner by the anterior pituitary
- Levels vary significantly with age, sex, and pubertal stage
- Both hormones show diurnal variation
- Random single measurements may be misleading due to pulsatile secretion
Normal Physiological Changes
Mini-Puberty of Infancy
- Peak levels occur between 1-3 months of age
- Boys: LH predominant
- Girls: FSH predominant
- Levels decline to prepubertal values by 6-9 months
Childhood
- Very low but detectable levels
- FSH typically slightly higher than LH
- Minimal diurnal variation
Puberty
- Initial rise in sleep-associated LH pulses
- Gradual increase in pulse amplitude and frequency
- FSH rises earlier but to a lesser degree than LH
Clinical Indications for Testing
Primary Indications
- Delayed puberty (>14 years in boys, >13 years in girls)
- Precocious puberty (<8 years in girls, <9 years in boys)
- Primary or secondary amenorrhea
- Suspected hypogonadism
- Disorders of sexual development (DSD)
Specific Clinical Scenarios
- Evaluation of cryptorchidism
- Investigation of ambiguous genitalia
- Monitoring of hormone replacement therapy
- Assessment of gonadal function post-chemotherapy
Age-Specific Reference Ranges
Infants (1-6 months)
- FSH:
- Males: 0.2-4.1 IU/L
- Females: 1.0-11.3 IU/L
- LH:
- Males: 0.5-6.0 IU/L
- Females: 0.1-3.3 IU/L
Prepubertal (>2 years)
- FSH:
- Males: <1.0 IU/L
- Females: <3.0 IU/L
- LH:
- Males: <0.6 IU/L
- Females: <0.3 IU/L
Pubertal
- FSH:
- Males: 1.5-12.4 IU/L
- Females: 1.0-8.4 IU/L
- LH:
- Males: 1.7-8.6 IU/L
- Females: 1.0-11.4 IU/L
Result Interpretation
High Gonadotropins
- Primary gonadal failure
- Turner syndrome
- Klinefelter syndrome
- Gonadal dysgenesis
- Post-chemotherapy/radiation
Low Gonadotropins
- Constitutional delay
- Hypogonadotropic hypogonadism
- Kallmann syndrome
- Hypopituitarism
- Chronic illness
LH:FSH Ratio
- >1: Suggests central precocious puberty
- <1: More common in prepubertal children
- Elevated in PCOS (adolescents)
Clinical Pearls
- Early morning sampling is preferred due to diurnal variation
- GnRH stimulation test may be needed for definitive diagnosis
- Multiple samples may be required due to pulsatile secretion
- Consider concurrent testosterone/estradiol measurement
- Interpret results in context of clinical findings and Tanner staging
- Ultrasensitive assays are preferred for prepubertal children
