Early treatment with GH alone in Turner syndrome: prepubertal catch-up growth and waning effect

OBJECTIVE: In order to ascertain the advantages of early GH treatment in Turner syndrome (TS), we started a prospective study aimed at evaluating prepubertal height gain in a cohort of 29 girls who were treated with the same pro-kilo GH dose (1.0 IU/kg per week) since they were less than 6 years old and for at least 5 years before entering puberty. PATIENTS AND DESIGN: Following a minimum of 6 months of baseline observations, 29 girls with TS were enrolled for this prospective study provided that they (a) were less than 6 years old, (b) were below -1.0 standard deviation score (SDS) for height, (c) had a projected adult height (PAH) lower than the respective target height (TH) and (d) had a height velocity (HV) lower than -1.0 SDS. All the selected girls underwent a 5-year treatment with biosynthetic GH at a stable dose of 1.0 IU/kg per week and were periodically measured during the treatment period in order to evaluate height, HV and PAH. RESULTS: After a dramatic acceleration during the 1st year, HV was attenuated during the subsequent years, reaching its nadir at the 5th year. Height deficiency under therapy progressively decreased from entry onwards, shifting from -2.4+/-0.7 to -1.0+/-1.2 SDS. In the same period, mean PAH progressively increased, although after 5 years it remained lower than the average TH. CONCLUSIONS: (a) An effective growth-promoting strategy in TS should be based on early GH treatment, as suggested by our results. (b) This strategy could result in a prepubertal normalization of height, thus allowing the appropriate timing for the induction of puberty. (c) An initial GH dose of 1.0 IU/kg per week may be suitable during the first years of therapy, as shown by our data documenting an important waning effect of GH therapy only after the 4th year of treatment. (d) No acceleration of bone maturation was observed under this treatment regimen.