In this retrospective study, we aimed to determine the effect of obesity on GnRH stimulation test, in cases with thelarche stage 2 and 3, and to investigate whether the cut-off values of peak LH values and peak LH/FSH ratios in diagnosing idiopathic central precocious puberty in overweight and obese girls compared to normal-weight girls. The gene discussed is GNRH1; the disease is precocious puberty.