Klinefelter syndrome occurs in 1 in 600 males and is a common cause of infertility in men. It appears scar tissue forms in these boys' testicles, leading to progressive destruction over their lifetimes. Advanced reproductive technology can be used to surgically retrieve sperm from these individuals, but these methods have a 50% failure rate in adult Klinefelter patients. Younger men have higher success rates, suggesting that adolescence and young adulthood may be the best time to extract sperm, but these techniques have not been studied in Klinefelter patients younger than 26 years of age. Additionally, there is currently no way to predict which Klinefelter patients will have success with these methods and which of them will not. This trial will explore sperm extraction in Klinefelter syndrome in an age range (12-25 years) that has never been studied, with the ultimate hope of improving the potential for fertility in these patients. The specific goals of this study are to determine the ideal age for sperm retrieval in Klinefelter patients and to establish factors that can be used to predict which of these patients will have a higher likelihood of success with advanced reproductive technology. The hypothesis is that younger Klinefelter patients will have higher sperm retrieval rates.

Inclusion Criteria:

• diagnosed 47,XXY (Klinefelter syndrome)
• 12-25 years of age

Exclusion Criteria:

• testosterone therapy within past 6 months
• history of surgery, injury, or infection in the testicle
• solitary testicle