ESPE Abstracts

Introduction: GnRH test is standard in confirming the diagnosis of central precocious puberty (CPP). However, GnRH (Relefact) is not always readily available in Serbia and several other countries. Two studies so far have assessed use of triptorelin in diagnosing CPP, with different sampling protocols, and in only one of these studies were triptorelin test findings compared to GnRH test findings.

Objective: To evaluate the diagnostic accuracy of triptorelin test compared to the GnRH test in girls with suspected CPP. Secondary objective was finding the optimal timing for blood sampling during triptorelin test. Study was officially approved by the Hospital Ethics Committee.

Method: Both triptorelin and GnRH tests were performed in all enrolled girls with premature breast development, within two weeks, in randomized order. After collection of baseline samples and administration of 100 μg of GnRH i.v. or 100 μg of triptorelin s.c, sampling times for FSH and LH were 30, 45 and 60 min for GnRH test; and 30, 60, 90, 120 and 180 min for triptorelin test, with additional 24 h sample for FSH, LH and estradiol. The diagnosis of CPP was made based on GnRH test LH peak ≥3.3 IU/l.

Results: Out of 14 girls with premature breast development which have enrolled and completed the study so far, five girls were diagnosed with premature thelarche (PT), and nine with CPP. Girls with CPP differed significantly from girls with PT regarding bone age advancement (+1.7±1.2 vs -0.1±1.1 years, P=0.012), had higher LH peaks during triptorelin test (16.3±20.1 vs 2.1±0.7 IU/l, P=0.002) and higher estradiol levels 24h after administration of triptorelin (782±457 vs 109±75 pmol/l, P=0.002). LH peak cutoff of ≥3.0 IU/l during triptorelin test showed 100% specificity and 89% sensitivity in detecting CPP. Using this cutoff resulted in missing one girl with CPP (LH peak during GnRH test 6.1 IU/l), which had non-progressive form of CPP with mild bone age advancement (+0.75 years). Lowering triptorelin LH peak cutoff to 2.6 IU/l would increase the sensitivity to 100%, reducing specificity to 60%.

Conclusion: Triptorelin test with LH peak cutoff ≥3.0 IU/l can be used as alternative test for diagnosing CPP. GnRH test should be performed in girls with triptorelin test LH peak <3.0 IU/l if they show advancement of bone age or other signs of pubertal progression during follow-up.