ESPE Abstracts (2015) 84 P-2-543

The Endocrine Response to a Gonadotropin Releasing Hormone (GnRH) Test: Establishing a Reference Interval in Healthy Girls below 6 Years of Age

Esben Vestergaarda,b, Mia Sømodc, Kostas Kamperisc, Karin Kastbergc, Søren Rittigc, Kurt Kristensenc & Niels Birkebækc

aAarhus University, Aarhus, Denmark; bRanders Regional Hospital, Randers, Denmark; cAarhus University Hospital, Aarhus, Denmark

Background: Premature thelarche and precocious puberty are frequently diagnosed even in girls below 6 years of age. A GnRH test is often included in the diagnostic work up. Interpretation of the GnRH test in girls below 6 years of age is, however, difficult, because the reference interval has not been established in this age group.

Objective and hypotheses: To establish the normal endocrine response to a GnRH test in healthy girls below 6 years of age.

Method: Thirty-six healthy girls aged 3.77 (range 0.85–5.99) years were included. Anthropometrics, Tanner stage, bone age, and baseline serum levels of estradiol and sex hormone binding globulin (SHBG) were determined. Each girl participated in a GnRH test: Blood samples for serum values of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were drawn before and 30 minutes after an i.v. injection of gonadorelin 0.1 mg/m2 (max 0.1 mg). LH, FSH, estradiol, and SHBG were measured by chemiluminescence immune-assay (Roche Cobas E601, module immunology analyzer).

Results: The 30 minute LH response (median and 95% CI) was 3.18 (2.55–3.62) Iu/l and the FSH response was 16.17 (13.59–17.91) Iu/l. Stimulated LH and FSH concentrations correlated inversely with age, r=−0.59 (P<0.001) and r=−0.42 (P=0.01), respectively. The stimulated LH/FSH ratio was 0.21 (95% CI 0.18–0.25, range 0.06–0.39) and did not correlate with age.

Conclusion: This clinical investigation reports the largest series of GnRH tests in healthy girls below 6 years of age. We provide a normal reference interval for the GnRH test in girls in this age group. Our data are of major clinical relevance when evaluating girls below 6 years of age with premature sexual characteristics.

Funding Information: This work was supported by Aarhus University, Institute of Clinical Medicine, The A.P. Møller Foundation, Søster og Verner Lipperts Fond, and Grosserer L. F. Foghts Fond.

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