Predictive factors for the effect of gonadotrophin releasing hormone analogue therapy on the height of girls with idiopathic central precocious puberty.

The factors influencing the final height of central precocious puberty patients treated with gonadotrophin releasing hormone (GnRH) analogues remain a critical issue. This study compares the predicted final height before and after GnRH analogue therapy to identify predictive factors for final height. Fourteen girls with idiopathic central precocious puberty were treated with a GnRH analogue. All had an active non-regressive form before therapy, full and permanent suppression of oestrogenic activity during therapy (duration greater than 2 years, 3.1 +/- 0.3 years, mean +/- SEM), and the pubertal pituitary-ovarian axis had normalized in all of them 1 year after the cessation of therapy. The mean predicted final height increased from 152 +/- 1.8 cm before therapy to 162.2 +/- 1.2 cm (P less than 0.01) at the last evaluation performed 4.5 +/- 0.3 years after the onset of therapy. The mean gain in predicted final height between the onset of therapy and the last evaluation was 10.2 +/- 1.1 cm. It was correlated with the following data recorded at the onset of therapy: bone age advance over chronological age (r = 0.66, P less than 0.02), predicted final height at the onset of therapy (r = -0.76, P less than 0.001), and the difference between the target height and the predicted height at onset of therapy (r = 0.76, P less than 0.001). We conclude that GnRH analogue therapy is more likely to improve final height prognosis in girls who initially present with a markedly advanced bone age and a great difference between their target and predicted heights. Both these parameters reflect the severity of the disease at diagnosis.