Patient Preparation: 2.5 µg/kg (up to 100 µg) of GnRh is given intravenously as a rapid IV bolus.
Specimen Collection: Two baseline serum samples are drawn 10 minutes apart prior to administration of GnRH. Serum samples are drawn every 15 minutes for 2 hours (8 samples).
Specimen Testing: Each sample is tested for LH and FSH.
Interpretation:
• normal pubertal or adult patients show an increase of LH 3-10 times baseline and FSH 1.5-3 times baseline, with peak levels occurring between 15-30 minutes after injection
• prepubertal children usually show no or minimal increases in LH and FSH, rarely above 2 times baseline
• postmenarche women show significant variability in response depending on stage of menstrual cycle
• patients with pituitary disorders may show absent, diminished or normal responses
• patients with hypothalamic disorders may show absent, diminished, normal or increased responses
• thus this test cannot reliably distinguish between pituitary and hypothalamic disorders
