Background Some studies have examined the effect of gonadal suppression on insulin-like growth factor-1 (IGF-1) levels and the growth velocity (GV) with conflicting results. Methods Forty-four girls treated with gonadotropin-releasing hormone analogue (GnRHa) for central precocious puberty (CPP) were included in the study. IGF-1 levels were examined at the beginning and after 12 months of treatment. Results IGF-1 and IGF-1 standard deviation score (SDS) according to chronological age (CA-IGF-1 SDS) at diagnosis were positively correlated with chronological age (CA), anthropometric measurements, stage of puberty, bone age (BA), BA-CA, follicle-stimulating hormone (FSH), luteinising hormone (LH), oestradiol, uterus length, endometrium thickness and ovarian volume (OV) at diagnosis (p < 0.05). There was no significant difference in IGF-1 levels after treatment. However, there was a negative correlation between ΔIGF-1 SDS and IGF-1 level, CA-IGF-1 SDS and BA-IGF-1 SDS at diagnosis (p < 0.05). There was no correlation between GV and IGF-1, ΔIGF-1. GV was negatively correlated with basal LH level at diagnosis (p = 0.008, r = -0.397). Peak LH levels of the patients who had GV-SDS < 0 were more suppressive than those of the patients who had GV-SDS > 0 after 12 months of treatment. Conclusions It was determined that the IGF-1 level and CA-IGF-1 SDS at baseline were correlated with more advanced pubertal stage prior to treatment. Initiation of treatment with a relatively high level of IGF-1 increased the risk of a decrease in the IGF-1 level. Likewise, the initiation of treatment with a relatively high LH level may increase the risk of low GV, but low GV was not related to the IGF-1 level. Increased sex steroid suppression may increase the risk of low GV.
Keywords: GnRHa treatment; IGF-1; growth velocity; precocious puberty.