Gonadotropin releasing hormone (GnRH) is secreted by the hypothalamus and results in release of both luteinizing hormone (LH) and follicle stimulating hormone (FSH). In patients with hypothalamic or pituitary disorders, serum levels of LH and FSH may be decreased. Measurement of LH and FSH is done before and after administration of GnRH to demonstrate pituitary release of gonadotropins.


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.



• 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


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