Muscle function improves during growth hormone therapy in short children born small for gestational age: results of a peripheral quantitative computed tomography study on body composition.
BACKGROUND
Short small for gestational age (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.


OBJECTIVE
Our aim was to investigate muscle-fat distribution and muscle function before and during GH treatment in short SGA children.


METHODS
A total of 34 prepubertal short SGA children (11 females, seven with Silver-Russell syndrome) were included in the study. Mean values were: age at GH start 7.3 yr; height sd score (SDS) -3.3; and birth weight SDS -2.7.


METHODS
Investigations over 24 months on GH treatment (57 microg/kg.d) were performed. Body composition, including fat area and muscle area (MA), was assessed through peripheral quantitative computed tomography (XCT 2000; Stratec, Inc., Pforzheim, Germany). Maximal isometric grip force was performed with a Jamar dynamometer (Preston, Jackson, MI). Comparison with height-dependent reference values (SDS(Height)) was calculated.


RESULTS
MA SDS(Height) at GH start was -1.8 and increased to -0.8 (P < 0.001) and -0.8, and fat area SDS(Height) decreased from -0.6 to -2.0 (P < 0.001) and -1.5 after 12 and 24 months on GH. Maximal isometric grip force 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 first year of GH treatment (R = -0.40; P < 0.001).


CONCLUSIONS
Short stature in SGA children is associated with low muscle mass and function. Supraphysiological GH doses led to a concomitant increment in height, muscle mass, and function, whereas fat mass decreased. Furthermore, body composition at GH start gives insight into GH responsiveness and the individual risk of metabolic syndrome.
Schweizer
Roland
R
Pediatric Endocrinology Section, University Hospital for Children and Adolescents, Hoppe Seyler Strasse 1, D-72076 Tuebingen, Germany. Roland.Schweizer@med.uni-tuebingen.de
Martin
David D
DD
Schönau
Eckhard
E
Ranke
Michael B
MB
D001823:Body Composition; D001827:Body Height / Q000187:drug effects; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D005260:Female; D006130:Growth Disorders / Q000188:drug therapy* / Q000503:physiopathology; D019382:Human Growth Hormone / Q000172:deficiency / Q000627:therapeutic use*; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D008297:Male; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology*; D014057:Tomography, X-Ray Computed
D019382:Human Growth Hormone