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EFFECT OF GONADOTROPIN-RELEASING HORMONE ANALOGUE ON THE SOMATOTROPIN AXES’ FUNCTION IN GIRLS WITH IDIOPATHIC CENTRAL PRECOCIOUS PUBERTY

Ma HM¹, Du Ml².

First Affiliated Hospital of Sun Yat-sen University of Medical Sciences, Guangzhou, China

Objectives: To recognize the changes in the somatotropin axe’s function of girls with Idiopathic central precocious puberty (ICPP) treated with Gonadotropin-releasing hormone analogue(GnRHa), and to probe into the cause of growth velocity reduction during GnRHa treatment.

Methods: 14 girls with ICPP were studied. Their growth velocity at the beginning and the end of 6-month of GnRHa treatment were observed. Maturation rates (MI) were got from vaginal smear, serum estradiol(E₂), insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) were determinated and the ratio of IGF-1 to IGFBP-3 were calculated at the beginning and the end of 6-month of GnRHa treatment. 13 age-matched healthy prepubertal girls served as controls.

Result: With 6-month GnRHa treatment, the growth velocity reduced significantly [(8.23±1.67)cm/y versus ( 6.27±1.54)cm/y，P=0.00091]. MI and serum E₂ concentration returned to prepubertal level. At the beginning of GnRHa treatment, serum IGF-1, IGFBP-3 concentration and IGF-1/IGFBP-3 were all markedly higher in ICPP girls as compared with the controls[(0.21±0.14)μg/ml, (4.04±0.51)μg/ml and 0.051±0.024)，P=0.000082, 0.023 and 0.00018 respectively]. After 6-month GnRHa treatment, serum IGF-1 and IGFBP-3 level remained high, moreover, serum IGFBP-3 tended to increase but not significantly[(5.29±1.24)μg/ml versus (4.91±1.17)μg/ml, P =0.063]. Neither serum IGF-1 level nor IGF-1/IGFBP-3 changed significantly[(0.49±0.15) μg/ml versus (0.49±0.16)μg/ml, P=0.98 and (0.093±0.020) versus (0.10±0.034), P=0.31 respectively].

Conclusion: GnRHa slows growth velocity in girls with ICPP, which doesn’t relate to the changes of serum blood free IGF-1 concentration. Changes in local IGF-1 and IGFBP-3 concentration in the growth plate or its IGF-1 receptor after GnRHa treatment were worth to be further studied.