Reduction of baseline body mass index under gonadotropin-suppressive therapy in girls with idiopathic precocious puberty

OBJECTIVE: To investigate longitudinally body mass index (BMI) evolution and obesity prevalence in a large and very homogeneous study population consisting only of girls with non-organic central precocious puberty (CPP) who were treated with gonadotropin-releasing hormone agonists (GnRHa) for at least two years. PATIENTS AND DESIGN: The 101 girls with idiopathic CPP who were selected for this study fulfilled the following inclusion criteria: (a) suppression of gonadotropin and gonadal sex steroid secretion during the overall GnRHa treatment period; (b) adequate compliance with the therapy regimen. All the girls were treated for 44+/-14 months and were followed-up for 15.7+/-7.8 months after therapy withdrawal. RESULTS: At the start of therapy, 23.8% of the girls had a BMI exceeding 2 standard deviation scores (SDS) and were therefore classified as obese; both average BMI-SDS and obesity prevalence significantly decreased during the treatment period (chi(2)=16.6, P<0.0005) and only 4% of the patients, all with pre-existing obesity, were still obese at the end of therapy; during the therapy period, BMI-SDS increased in none of the patients. Both average BMI-SDS and obesity prevalence (from 4 to 0%; chi(2)=4.0, P<0.05) further decreased during the period that followed therapy withdrawal. CONCLUSIONS: (a) girls with idiopathic CPP are frequently obese at the onset of GnRHa therapy (23.8%), probably due to the hormonal changes which accompany the start of puberty; (b) their obesity is neither long-lasting nor related to GnRHa administration; (c) on the contrary, GnRHa therapy may have a favourable effect on BMI decrease, provided that treatment is performed for at least two years and is accompanied by a complete suppression of gonadotropin secretion; (d) this unexpected effect, which has never been reported hitherto, might represent a further indication for GnRHa administration in idiopathic CPP.