Objectives: There is a complex interaction between the anti-mullerian hormone (AMH) and hypothalamic-pitui-tary-gonadal axis. However, the effect of gonadotropinreleasing hormone (GnRH) stimulation on AMH levels is not clearly known. In the study, we aimed to evaluate the effect of GnRH stimulation on AMH levels in central precocious puberty (CPP) and isolated premature thelarche (PT) groups. Methods: Sixty-three girls with breast development before the age of 8 were enrolled in the study. GnRH test was performed on all subjects. Blood samples for follicle stimulating hormone (FSH), luteinizing hormone (LH), and AMH levels were taken at basal, 40th, and 90th minute of GnRH test. Subjects were grouped as CPP and PT group. Results: After GnRH stimulation, AMH levels increased significantly at the 40th minute and the stimulating effect of GnRH on AMH continued till the 90th minute (p: 0.0001). There was a positive correlation between basal and 90th minute AMH levels (r: 479, p: 0.0001). The highest FSH, LH, and AMH times were significantly different after the GnRH stimulation (p: 0.001, p: 0.001, and p: 0.007). Although the CPP group had a lower basal AMH level than the PT group's basal AMH level; AMH response to GnRH stimulation was not different (p>0.05). Conclusions: In our study, which examined the effect of GnRH stimulation on AMH levels in early pubertal development disorders for the first time, GnRH stimulated AMH secretion rapidly, correlated with basal AMH. Basal AMH levels were lower in patients with CPP than in those with PT; however, the effect of GnRH stimulation on AMH levels was similar in both groups.