Turner syndrome is a condition in which a female's breasts, vagina, and uterus do not fully develop and puberty does not occur. Females with Turner syndrome may also have heart problems at birth, have learning disabilities, and end up much shorter than other members of their family.

Normally, a female has two X chromosomes. Females with Turner syndrome are missing all or part of one X chromosome. This affects sexual development and lowers the production of female hormones.

Turner syndrome is also called gonadal dysgenesis or monosomy X.