Preserving adult height potential in girls with idiopathic true precocious puberty

We designed a prospective study of height potential in giris with idiopathic precocious puberty, comparing the presenting features of giris with and without evidence of reduced adult height potential. The 14 giris with impaired adult helght prognoses (group 1) were reexamined after treatment with a gonadotropin releasing hormone agonist, nafarelin. The seven giris with the prognosis of unimpaired height (group 2) were followed without therapy. We found that the group could be distinguished at initial examination by the greater bone age/height age ratio of group 1 (mean ± SEM: 1.4 ± 0.06 vs 1.0 ± 0.05; p <0.005) and by the greater difference between predicted height and target height in group 1. The mean predicted height in group 1 was significantly less than the mean target height (150.7 ± 2.1 vs 165.4 ± 3.0 cm; p<0.005), whereas the mean predicted and target heights in group 2 were similar (165.4 ± 3.0 vs 164.3 ± 2.1 cm). Initial estradiol levels were also greater in group 1 than in group 2 (21.6 vs 10.6 pg/ml; p<0.05), although this difference was not sustained during follow-up. In group 1, nafarelin therapy suppressed the pltuitary-gonadal axis, and although there was a transient reduction in height potential in giris with the youngest bone ages during the first 6 months of therapy, 2 years of treatment slightly improved predicted heights from 150.7 ± 2.1 to 152.7 ± 2.0 cm (p<0.05). Height predictions also increased without therapy during the 2-year observation period in group 2, from 165.4 ± 3.0 to 168.7 ± 4.1 cm (p<0.05). Our data indicate that gonadotropin releasing hormone agonist therapy preserves height potential in giris with an initially impaired height prognosis, and that height potential is preserved without therapy in those with a good initial height prognosis.