Background: Short SGA children can be affected by a lack of muscle mass rather than fat mass. They also face a high risk of the metabolic syndrome developing after childhood. It is not known whether low muscle mass influences muscle function.

Aim: Investigating muscle-fat distribution and muscle function before and during GH treatment in short SGA children.

Patients: 34 prepubertal short SGA children (11 female, 7 Silver Russell). Mean values: age at GH start 7.3 yrs; height [SDS] –3.3; birth weight [SDS] –2.7.

Methods: Investigations over 24 months on GH treatment (57 µg/kg/d). Body composition; fat area (FA), muscle area (MA) assessed through pQCT (XCT 2000). Maximal isometric grip force [MIGF] with a Jamar dynamometer. Comparison with height-dependent reference values ([SDS]_Height).

Results: MA [SDS]_Height at GH start: -1.8, increased to -0.8 (p <0.001) and -0.8, FA [SDS]_Height decreased from –0.6 to –2.0 (p <0.001) and –1.5 after 12 and 24 months on GH. MIGF [SDS]_Height increased from –0.9 to 0.3 (p <0.001) and 0.5. MA at start correlated negatively with height velocity (R = -0.54, p <0.001) and MA [SDS] at start and delta height [SDS] during the 1st year of GH treatment (R = -0.40, p <0.001).

Conclusion: Short stature in SGA children is associated with low muscle mass and function. Supra-physiological GH doses led to a concomitant increment in height, muscle mass and function, while fat mass decreased. Furthermore, body composition at GH start gives insight into GH responsiveness and the individual risk of metabolic syndrome.