Turner syndrome: a review of genetic and hormonal influences on neuropsychological functioning.

Turner syndrome (TS) is a genetic disorder affecting mainly females that arises from a loss of X chromosome material, most usually one of the two X chromosomes. TS is associated with a number of characteristic physical features such as short stature and absent ovaries as well as a set of common neuropsychological deficits and social and behavioral features. This paper will serve to review the cognitive, social, and psychoeducational abilities of individuals with TS as well as neuroimaging findings. Several putative genetic mechanisms contributing to their particular neurocognitive deficits will also be described including candidate genes. In addition, the available evidence on how hormones affect specific abilities in TS will be reviewed. It will be concluded that the TS neurobehavioral profile arises from an atypical cerebral organization caused by the complex interplay of insufficient expression of certain (unknown) genes on the X chromosome and by abnormal hormonal levels; however, it is still not clear exactly how the specific genes affect broader cognitive abilities. Future research needs to identify the elemental processes that are disturbed in TS and map these both to events in early brain development and subsequent brain function and to specific gene and hormonal contributions.