September 24, 2017
Gonadotropin Releasing Hormone (GnRH) Test Minimize

Gonadotropin releasing hormone test

Indication

To diagnose hypothalamic-pituitary disease in precocious and delayed puberty in both sexes in those children with low basal gonadotropins.

Contra-indications

This test may be performed simultaneously with TRH or glucagon as part of triple pituitary test.

Principle

GnRH (gonadotropin releasing hormone) is a decapeptide secreted by the hypothalamus which stimulates the production and secretion of LH and FSH by the anterior pituitary.

Side effects

GnRH may rarely cause nausea, headache and abdominal pain.

Preparation

no specific patient preparation is required.

Requirements

3 serum tubes
GnRH the dose for children is 2.5 microgm/kg to a max 100 microgm

Procedure

time 0 min

take 2 mL blood for LH & FSH and testosterone (males) or oestradiol (females)
immediately give GnRH iv as a bolus (dose as above)

time 20 min

take 2 mL blood for LH & FSH

time 60 min

take 2 mL blood for LH & FSH

Interpretation

  1. Normal basal reference values in prepubertal children are:
    LH < 2.0 iu/L
    FSH < 2.0 iu/L
  2. Following GnRH, the response may be considered normal if the basal values are in the reference range and there is at least a doubling at 20 min for LH and FSH. The response varies throughout the menstrual cycle: early (D4) < late follicular (D11) = "luteal" (D21), max response occurs at the mid-cycle (D14).
  3. An exaggerated response is seen in primary & secondary gonadal failure.
  4. A flat response in gonadotropins (< 5 iu/L) occurs in prepubertal children and with pituitary and/or hypothalamic disease. However, a normal response does NOT exclude pituitary or hypothalamic disease since the response will be affected by the exact anatomy of the disorder.
  5. The magnitude of the LH response is proportional to the mean nocturnal LH and therefore the evolution of puberty.

References

  • Wu FCW, Butler GE, Kelnar CJH, Sellar RE. Patterns of pulsatile luteinizing hormone secretion before and during the onset of puberty in boys: a study using an immunoradiometric assay. J Clin Endocrinol Metab 1990;70:629-637.
  • Yen SSC, VandenBerg G, Rebar R, Ehara Y. Variations in pituitary response to synthetic LRF during different phases of the menstrual cycle. J Clin Endocrinol Metab 1972;35:931-7.

JHB 22 Sept 2011

  

Home|Paediatric|Endocrinology|Renal & electrolytes|Metabolic|Investigation protocols|Misc
Comments about this site to julian.barth@nhs.net Terms Of Use Privacy Statement