EFFECT OF DESLORELIN DOSE IN THE TREATMENT OF CENTRAL PRECOCIOUS PUBERTY

Central precocious puberty is effectively treated with long-acting LHRH analogs (LHRHas). Although at least six LHRHas have now been used in children, there have been no studies to determine the least effective dose of any of these analogs. We sought to determine the effect of decreasing an efficacious dose of deslorelin (D-Trp6-Pro9-NEt-LHRH) on basal and LHRH-stimulated gonadotropins, estradiol levels, and the rates of linear growth and skeletal maturation in subjects with central precocious puberty. Twenty-nine children with central precocious puberty were enrolled in a double blinded study. All subjects were treated for the initial 3 months with deslorelin at a dose (4-mu-g/kg.day, sc) known to suppress gonadotropins, linear growth velocity, and the rate of skeletal maturation. After 3 months, the subjects were randomly assigned to receive one of three daily sc doses of deslorelin: 4-mu-g/kg (n = 9), 2-mu-g/kg (n = 11), or 1-mu-g/kg (n = 9). They were treated at this dose in double blinded fashion for 15 months, after which time they resumed therapy at a dose of 4-mu-g/kg.day for an additional year. The children in the three groups did not differ in terms of chronological age, bone age, pretreatment growth rate, or Tanner stage at the onset of therapy. Similarly, there were no differences in the clinical and hormonal responses to the first 3 months of LHRHa therapy (4-mu-g/kg.day). During the 15-month period at the three different doses, the three dose groups could not be distinguished from each other in terms of pubertal stage, linear growth velocity, rate of skeletal maturation, sex steroid levels, mean LH or FSH levels, or peak FSH response to LHRH stimulation or to a dose of deslorelin. In contrast, the peak LH response to LHRH stimulation was highest in children treated with the lowest dose (1-mu-g/kg.day; P < 0.025, by multiple analysis of variance). In addition, the peak LH response to a dose of deslorelin (the LHRHa test) was higher in children treated with 1-mu-g/kg.day than in those treated with 4-mu-g/kg.day (P < 0.04). In summary, the LHRHa test is a sensitive means for detecting activation of the hypothalamic-pituitary-gonadal axis, and deslorelin at a dose of 1-mu-g/kg.day results in less gonadotropin suppression than a dose of 4-mu-g/kg.day. Based on these short term data, we hypothesize that deslorelin at a dose of 2-mu-g/kg.day has efficacy similar to that of the dose of 4-mu-g/kg.day. However, since no significant toxicity has been reported at the 4-mu-g/kg.day dose and until a longer term study can be performed in larger numbers of children, we continue to recommend that deslorelin be used at the dose of 4-mu-g/kg.day because of the more extensive data on treatment outcome that are available at this dose. In summary, the LHrha test is a sensitive means for detecting activation of the hypothalamic-pituitary-gonadal axis, and deslorelin at a dose of 1-mu-g/kg.day results in less gonadotropin suppression than a dose of 4-mu-g/kg.day. Based on these short term data, we hypothesize that deslorelin at a dose of 2-mu-g/kg.day has efficacy similar to that of the dose of 4-mu-g/kg.day. However, since no significant toxicity has been reported at the 4-mu-g/kg.day dose and until a longer term study can be performed in larger numbers of children, we continue to recommend that deslorelin be used at the dose of 4-mu-g/kg.day because of the more extensive data on treatment outcome that are available at this dose.