Gonadotrophin-releasing hormone analogues as therapeutic probes in human growth and development: evidence from children with central precocious puberty.

Statural growth and skeletal development were assessed in 87 girls with idiopathic central precocious puberty (CPP) during gonadotrophin-releasing hormone analogue (GnRHa)-induced suppression of gonadarche. Before the start of therapy, mean chronological age (CA) was 6.3 years and mean bone age (BA) was 10.6 years. During up to 6 consecutive years of complete suppression of gonadal sex steroid secretion, the mean height velocity decreased from 10.8 cm/year to prepubertal rates. At each interval height velocity was found to be inversely and negatively correlated with BA such that girls with advanced BAs grew at rates well below prepubertal norms but appropriately for their degree of skeletal maturation. Skeletal maturation similarly slowed during prolonged GnRHa administration (delta BA/delta CA = 0.6 +/- 0.1 over 3 years, mean +/- SD, n = 66) and was also negatively correlated with the BA before the start of therapy. Predicted adult height increased progressively during therapy; however, when analysed as changes in height SDS(BA), the impact of treatment was variable and correlated positively with the initial degree of skeletal maturation. The effect of GnRHa therapy on growth in children with CPP requires long-term study and is best analysed by employing a developmental perspective.