Abstract: Objective: To explore the value of ultrasound in diagnosing idiopathic central precocious puberty through study on the relationship between serum E2, FSH, LH levels and morphologic changes of uterus and ovary. Methods: Thirty-six girls with precocious puberty accepted GnRH stimulation tests and pelvic ultrasound examinations .The levels of E2, TSH, LH before injection and after 30, 60 minutes , and ovarian volume , uterine volume ,maximum follicular diameter were reviewed and analysed. Results: (1) Among the three types of ovaries (type1, homogeneous type ; type 2 , small follicular type ; type 3, large follicular type ), differences of the serum LH ,E2 levels and the ratio of LH∕FSH after GnRH 30 minutes and 60 minutes were significant (p<0.05).(2) The maximal follicular diameter was correlated to the serum LH ,E2,the ratio of LH∕FSH after GnRH 30 minutes and 60 minutes and the volume of ovary. (3) The volume of uterus was correlated to the serum LH,E2 levels and the ratio of LH∕FSH after GnRH 30 minutes and 60 minutes. (4) The volume of ovary was correlated to the serum LH levels and the ratio of LH∕FSH after GnRH 30 minutes and 60 minutes. Conclusion: (1)There was close relationship between LH levels and follicular development .It also proved that serum E2 levels was mainly decided by the development status of the follicles.(2)The volume of uterus was significantly correlated to E2 levels. Development of uterus was estrogen-dependent. (3)Judgement based on GnRH stimulation test and morphologic changes of uterus and ovary would be crucial for establishing the diagnosis of idiopathic central precocious puberty.

Key words: Precocious puberty, Uterus, Ovary, GnRH stimulation test, serum E2