Subnormal Growth Velocity and Related Factors During GnRH Analog Therapy for Idiopathic Central Precocious Puberty

OBJECTIVE: Data concerning subnormal growth velocity (GV) and factors that influence this during gonadotropin-releasing hormone analog (GnRHa) therapy for idiopathic central precocious puberty (ICPP) are scarce. We investigated the incidence of subnormal GV and associated factors in patients receiving GnRHa therapy for ICPP. METHODS: In this retrospective cohort study, the records of 50 girls who had been diagnosed with ICPP and started on GnRHa treatment before the age of eight years were investigated. Subnormal GV frequency, related factors during GnRHa therapy and the effect on final height were examined. RESULTS: During the treatment, a significant decrease in the annual GV and GV standard deviation score (SDS) of the patients was observed. In 16 (32%) patients GV never declined below -1 SDS, while a decline was noted once and twice in 19 (38%) and 15 (30%) patients respectively. The median age of detection of subnormal GV was 9.9 (4.9-10.9) years. Patients with pubic hair at diagnosis were found to have an increased risk of subnormal GV (p=0.016). There was a significant negative correlation between diagnostic basal luteinizing hormone (LH) level and the first and second year GV SDS (p=0.012 and 0.017 respectively). A significant negative correlation between bone age at diagnosis and 3(rd) year GV SDS, and 4(th) year GV SDS (p=0.002 and p=0.038) was also observed. LH suppression significantly increased during treatment (p=0.001). CONCLUSION: In girls with ICPP the risk of subnormal GV appears highest at the 3(rd) year of GnRHa treatment, particularly in those patients with, at the time of diagnosis, pubic hair in conjunction with high baseline and peak LH and advanced BA and excessive LH suppression on follow-up.