Klinefelter syndrome (KS) is a genetic condition that affects males. It occurs when a male is born with an extra X chromosome, resulting in the karyotype 47,XXY rather than the typical 46,XY. This additional genetic material can impact various aspects of development and health, often leading to a spectrum of physical, cognitive, and reproductive issues. One of the primary treatments for managing some of the symptoms associated with Klinefelter syndrome is testosterone replacement therapy (TRT). The Basics of Klinefelter Syndrome Klinefelter syndrome is named after Dr. Harry Klinefelter, who first described the condition in 1942. It is one of the most common chromosomal abnormalities, occurring in approximately 1 in 500 to 1,000 live male births. Genetic Basis and Diagnosis KS is typically caused by nondisjunction during meiotic division, leading to an extra X chromosome. This results in a 47,XXY karyotype, though variants such as 48,XXXY or mosaic patterns (46,XY/47,XXY) ca