GNRH1 and central precocious puberty: GnRH stimulation tests confirmed CPP cases. The mean IGF1 and IGF1-SDS levels were significantly greater in CPP patients (270.15 ng/mL; 1.943 SDS) than in NP-CPP patients (174.12 ng/mL; 0.788 SDS) and controls (139.28 ng/mL; 0.208 SDS) (p < 0.001).