When to stop GnRH analog therapy: the experience of the italian study group for physiopathology of puberty.

Data reported in this study have been recently published elsewhere. The authors retrospectively analyzed the auxological response to GnRH agonist treatment and the final height (FH) outcome in 71 girls with idiopathic and truly precocious (onset before 8 years) central puberty (CTPP), who had been treated with the same therapy protocol (Decapeptyl Depot at the dose of 60 microg/kg i.m. every 28 days) for at least 2 years (since 7.0 +/- 1.3 yr) and followed until puberty was completed and FH was reached. During the entire treatment period we observed: A) a decrease of height standard deviation scores (SDS) (from 1.5+/-1.7 to 0.9+/-1.3 SDS, p<0.01); B) a striking deceleration of BA, revealed by the subnormal deltaBA:deltaCA ratio (0.2 +/- 0.1); C) an increase of predicted adult height (from 155.6+/-7.0 to 160.7+/-6.7 cm, p<0.0005). Treatment interruption was followed by notable catchdown growth, with FH (158.4 +/- 5.8 cm) lower (p < 0.025) with respect to that predicted at the end of therapy. However FH fell within the population norm and the target range in 87.3% and 90% of patients, respectively. The tallest FH was recorded in the patients who discontinued treatment at a BA of 12.0-12.5 years. We conclude that: 1) Most girls with idiopathic CTPP treated by GnRH agonists may achieve an adult height within the population norm and/or their target range; 2) The height gain from therapy onset until FH attainment, however, is generally rather limited (on average 2.9 cm) and only few patients are able to reach their target percentile; 3) The most favorable height prognosis with respect to target height (TH) is generally observed in the patients with the tallest H2 and the lowest BA2:CA2 ratio, due to the notable deterioration of height prognosis which frequently follows therapy interruption; 4) In order to strengthen the weak therapeutic effect of GnRH agonists in CTPP, this treatment should be discontinued at a BA of 12-12.5 years.