Predictive factors for height gain in idiopathic central precocious puberty treated with GnRH analogues

PURPOSE: to evaluate predictive factors of response to GnRHa treatment in girls with idiopathic central precocious puberty. METHODS: a retrospective cohort study was conducted involving 33 girls diagnosed with idiopathic central precocious puberty and treated with GnRHa. The following independent variables were assessed: age at the beginning of therapy and at the onset of symptoms, time elapsed since the appearance of pubertal characteristics and the beginning of treatment, bone age, bone age advance, duration of GnRHa treatment, actual height and Z-score, predicted height and Z-score and hormone measurements of FSH and LH after GnRH stimulation, which were correlated with gain in height as a dependent variable at treatment discontinuation, calculated by the difference between the predicted height at the end and beginning of treatment. For statistical analysis, Pearson's linear correlation was used, in addition to multiple linear regression analysis. RESULTS: the mean age at the beginning of treatment was 7.8 +/- 1.3 years, with a mean bone age of 10.1 +/- 1.6 years. Bone age advance was 2.3 +/- 1.1 years and was controlled during the treatment period. Gain in predicted height was 2.5 +/- 1.3cm. It was positively correlated with time elapsed since the beginning of symptoms and the beginning of treatment and with bone age advance, while negatively correlated with the Z-score of height at the beginning of treatment and predicted height at the beginning of treatment, and the latter was the main factor determining gain from treatment. CONCLUSIONS: girls who had the most significant compromise of predicted adult height, as detected by a larger deviation from the population (Z-score) and the most considerable advance in bone age, received benefit from GnRHa therapy, and they must not be excluded from the group to be treated.