The Influence of GnRH Analog Therapy on Growth in Central Precocious Puberty

Children with central precocious puberty (CPP) present various somatic and psychological abnormalities.

The aim of the study was to evaluate growth changes in girls with central precocious puberty treated with GnRH analog therapy and to analyze the factors affecting the auxological response to this treatment.

The study group consisted of 40 girls with puberty onset aged 6.0 ± 1.9 years (mean, ± SD), treated with 3.75 mg decapeptyl depot intramuscularly every 28 days. The treatment was initiated at the age of 7.5 ± 2.2 years and continued for 3.3 ± 2.3 years, until the age of 11.4 ± 0.9 years. Height (Ht), height standard deviation score (HtSDS), statural age, bone age and Ht prediction.

During the treatment a decline in HtSDS from 2.0 ± 1.36 to 1.24 ± 1.0 was observed (p = 0.0002); and a deceleration in the maturation of bones of 1.0 ± 0.29 year in the first year and 0.66 ± 0.33 year in the following years (p = 0.0008). The HtSDS at the end of the treatment was significantly higher than was predicted in pretreatment (1.33 ± 1.04 vs. 0.07 ± 1.39, p = 0.0005). Ht and HtSDS after treatment were positively correlated with the predicted Ht (PAH) before treatment and negatively correlated with the bone age/statural age ratio before treatment (p < 0.05). The PAH before and after treatment correlated inversely with the bone age/statural age ratio (p < 0.05). Two subgroups were analyzed according to the patients' age when therapy was introduced: group 1 included girls who were under the age of 7 when therapy was introduced, and group 2 included girls aged 7 or older. There was a statistically significant difference in the PAH SDS before treatment between these two subgroups: Group I (-) 1.3 ± 1.8 vs. Group II (-) 0.14 ± 1.2 and there was no difference in the PAH SDS after treatment: Group I (-) 0.7 ± 1.1 vs. Group II 0.31 ± 1.2.

The child's age at the beginning of GnRHa therapy was an important predictor of height prognosis; the therapy introduced under the age of 7 improves the PAH during treatment. Height prediction during the entire treatment period is worse in children with more advanced bone age for their statural age at the onset of treatment.