In our population we found 31% of girls with suspected CPP and basal LH < 0.14 mIU/mL, among these 9.4% were false negatives and this implies that they will undergo a GnRH stimulation test later, during the follow up, allowing us to save 21.6% of useless GnRH tests. The gene discussed is GNRH1; the disease is central precocious puberty.