Association between foot growth and musculoskeletal loading in children with Prader-Willi syndrome before and during growth hormone treatment.

OBJECTIVE: To explore how foot growth relates to musculoskeletal loading in children with Prader-Willi syndrome (PWS). STUDY DESIGN: In 37 children with PWS, foot length (FL) before and after 6 years of growth hormone therapy (GHT) was retrospectively evaluated with parental and sibling's FL, height, and factors reflecting musculoskeletal loading, such as weight for height (WfH), lean body mass (LBM; dual energy X-ray absorptiometry, deuterium labeled water), physical activity (accellerometry), and walk age. Because of the typically biphasic evolution of body mass and the late walk age in PWS, 2 age groups were separated (group 1, >2.5 years; group 2, < or =2.5 years). RESULTS: Children with PWS normalized height, but not FL after 6 years of GHT. Parental FL correlation with PWS's FL was lower than with sibling's FL. In group 1, FL positively correlated with WfH, LBM, and physical activity. In group 2, FL negatively correlated with age at onset of independent ambulation. Foot catch-up growth with GHT was slower in group 2 compared with group 1. CONCLUSION: In PWS, FL is positively associated with musculoskeletal loading. Small feet in children with PWS before and during long-term GHT may be more than just another dysmorphic feature, but may possibly reflect decreased musculoskeletal loading influencing foot growth and genetic and endocrine factors.

Growth hormone and body composition in children younger than 2 years with Prader-Willi syndrome.

OBJECTIVES: To assess body composition of infants with Prader-Willi syndrome (PWS) by using deuterium dilution and investigating the efficacy of early institution of growth hormone (GH) therapy in increasing lean mass (LM) and preventing massive obesity. STUDY DESIGN: One group of 11 children with PWS <2 years before and during 30-month GH therapy (GH group) was compared with 6 infants administered only coenzyme Q(10) for 1 year (Q10 group). LM adjusted for height (LM(Ht)) and relative fat mass (%FM(Age)) standard deviation scores (SDS) were calculated from data of 95 healthy children. RESULTS: Initially, LM(Ht) of all patients was below the normal average. LM(Ht) decreased by -0.46 +/- 0.3 SD (P=.03) per year in the Q10 group but rose by 0.25 +/- 0.3 SD (P=.02) per year during GH therapy, normalizing after 30 months (-0.70 +/- 1.0 SD). Despite low to normal weight for height (WfH), %FM(Age) was above the normal average (GH group, 31.0% +/- 4.5%, Q10 group, 32.4% +/- 9.5%). In the Q10 infants, %FM(Age) increased by 0.71 +/- 0.7 SD per year, whereas in the GH group, %FM(Age) remained more stable up to 30 months. CONCLUSIONS: Diminished LM(Ht) found in infants with PWS further declines during the early years. Early institution of GH therapy lifts LM(Ht) into the normal range and delays fat tissue accumulation.

Improving body composition and physical activity in Prader-Willi Syndrome.

OBJECTIVE: To determine if muscle training in Prader-Willi Syndrome (PWS) can improve local body composition, physical capacity, and activity. STUDY DESIGN: Seventeen children and adolescents with PWS and 18 control children were enrolled in a daily short calf muscle training program for 3 months. Before (t(0)) and after 3 months of training (t(3m)), spontaneous physical activity and exercise capacity were assessed by pedometer registrations and activity protocols. Local body composition was determined by calf circumference and skinfold measurements at t(0), t(3m), and 3 months after t(3m) (t(6m)). RESULTS: During training, calf skinfold decreased from 1.1 to 0.8 SD (P <.01) and calf circumference in PWS increased from 1.4 to 1.9 SD (P <.05), reflecting improved muscle mass. At t(3m), a significant increase in spontaneous physical activity (from 45% to 71%, compared with baseline data of control children, P <.05) and physical capacity (from 31%-78%, P <.01) was found. CONCLUSIONS: In persons with PWS, a well-defined and easy-to-accomplish training program improves local body composition and has generalized effects on physical activity and capacity, opening up a new therapeutic option to improve metabolic conditions.