Clinical meaning
Turner syndrome is a chromosomal disorder affecting approximately 1 in 2,000 to 2,500 live female births, caused by complete or partial absence of one X chromosome, resulting in a 45,X karyotype. During normal female development, two X chromosomes (46,XX) are required for complete ovarian development and the full expression of female secondary sexual characteristics. In Turner syndrome, the missing or structurally abnormal X chromosome leads to gonadal dysgenesis, where the ovaries fail to develop normally and instead become fibrous streaks of connective tissue (streak gonads) incapable of producing adequate estrogen and progesterone. This ovarian failure results in primary amenorrhea, absent puberty, and infertility in most affected individuals. The haploinsufficiency of the SHOX gene (Short Stature Homeobox gene), which is located on the pseudoautosomal region of the X chromosome, is directly responsible for the characteristic short stature seen in Turner syndrome. SHOX normally promotes long bone growth, and with only one functional copy, skeletal growth is significantly impaired. The average untreated adult height is approximately 143 cm (4 feet 8 inches). Turner syndrome affects multiple organ systems beyond the reproductive system....