• Evaluation of several aspects of motor function including muscle strength, motor response speed, simple repetitive movement, and complex nonrepetitive motor action, previously shown to be impaired in boys with Klinefelter syndrome. [ Time Frame: 2 years per subject ] [ Designated as safety issue: Yes ]
  

Klinefelter syndrome (KS), a genetic disorder that affects males only, is characterized by having an extra X chromosome. The phenotype — or physical and learning features — includes testicular failure, tall stature, and specific cognitive and behavioral attributes such as diminished motor function, language-based learning difficulties, poor self-image, and shyness. The KS phenotype may be the result of androgen deficiency in utero, infancy, and childhood. For individuals with KS, androgen replacement is standard treatment in adolescence and adulthood but has not been used earlier in childhood or included in the standard medical care of KS children ages 4 to 12.

The purpose of this study is to examine the effects of androgen on learning and development in boys with KS. Researchers also want to determine if low-dose androgen replacement at an early age will improve some of the learning difficulties associated with the disorder. The overall goal of this study is to address questions regarding the relationship of early androgen deficiency to learning and motor function.

Participants in the study will be randomized to one of two treatment groups, receiving either oxandrolone (low-dose androgen) or placebo, for two years. All participants will be evaluated for safety at the beginning of the study and at 3, 6, 12, 18, and 24 months. Also at the beginning of the study and every 3 to 6 months thereafter (for a total of 6 visits), the researchers will perform a careful history and physical examination and a bone age X-ray, and obtain a blood sample.

Participation in the trial will last two years and includes 6 clinic visits.