Bone mineral density in children and adolescents with Prader-Willi syndrome: a longitudinal study during puberty and 9 years of growth hormone treatment.

CONTEXT: Longitudinal data on bone mineral density (BMD) in children and adolescents with Prader-Willi Syndrome (PWS) during long-term GH treatment are not available. OBJECTIVE: This study aimed to determine effects of long-term GH treatment and puberty on BMD of total body (BMDTB), lumbar spine (BMDLS), and bone mineral apparent density of the lumbar spine (BMADLS) in children with PWS. DESIGN AND SETTING: This was a prospective longitudinal study of a Dutch PWS cohort. PARTICIPANTS: Seventy-seven children with PWS who remained prepubertal during GH treatment for 4 years and 64 children with PWS who received GH treatment for 9 years participated in the study. INTERVENTION: The children received GH treatment, 1 mg/m(2)/day (≅ 0.035 mg/kg/d). MAIN OUTCOME MEASURES: BMDTB, BMDLS, and BMADLS was measured by using the same dual-energy x-ray absorptiometry machine for all annual measurements. RESULTS: In the prepubertal group, BMDTB standard deviation score (SDS) and BMDLSSDS significantly increased during 4 years of GH treatment whereas BMADLSSDS remained stable. During adolescence, BMDTBSDS and BMADLSSDS decreased significantly, in girls from the age of 11 years and in boys from the ages of 14 and 16 years, respectively, but all BMD parameters remained within the normal range. Higher Tanner stages tended to be associated with lower BMDTBSDS (P = .083) and a significantly lower BMADLSSDS (P = .016). After 9 years of GH treatment, lean body mass SDS was the most powerful predictor of BMDTBSDS and BMDLSSDS in adolescents with PWS. CONCLUSIONS: This long-term GH study demonstrates that BMDTB, BMDLS, and BMADLS remain stable in prepubertal children with PWS but decreases during adolescence, parallel to incomplete pubertal development. Based on our findings, clinicians should start sex hormone therapy from the age of 11 years in girls and 14 years in boys unless there is a normal progression of puberty.