Which parameters predict the beneficial effect of GnRHa treatment on height in girls with central precocious puberty?

Objective: Data about GnRHa on adult height in girls with central precocious puberty (CPP) have shown variable results, ranging from improvement of growth prognosis to lack of any benefit. This study was designed to delineate the criteria to decide which girls with idiopathic CPP (iCPP) will have a height benefit from GnRHa treatment. Design: Retrospective. Patients: 102 girls with iCPP who had reached final height (FH) were included. Measurements: Auxological, hormonal and radiological findings at treatment onset, and FHs were extracted from records. Results: Most important factor affecting height gain was chronological age (CA) at treatment onset. All the girls treated ≤6.4 years of age achieved a height gain of ≥1SDS, while none of the girls treated ≥8.3 years of age made the target. 75.6% of patients who started GnRHa between the ages of 6.4 and 8.3 years had a height gain of ≥1SDS. Most important factors affecting height gain in those treated 6.4-8.3 years were advanced bone age (BA), basal estradiol (E₂) and pubertal stage (r²: 0.906; P <.001). All individuals with BA advancement of ≥2.6 years or E₂ of ≥32.6 pg/ml or pubertal stage of ≥3 had significant height gain, and none of the cases with BA advancement of <2 years or E₂ of <21.5 pg/ml or pubertal stage of <2 had a height gain of ≥1SDS. Conclusions: Treatment with GnRHa is unquestionably beneficial to improve FH in girls with iCPP when initiated ≤6.4 years of age. GnRHa treatment after 8.3 years of age may not improve FH. Girls between the ages of 6.4 and 8.3 years at presentation can have a better height gain if BA (≥2.6 years over CA) and pubertal findings (pubertal stage ≥3 or E₂ ≥32.6 pg/ml) are well-advanced.