What is intersex?

During a typical conception, a sperm carrying either an X or Y chromosome fertilizes an egg, which already has an X chromosome. An XY pairing is a boy; an XX chromosome pairing is a girl.

Abnormalities in the genes on these or other chromosomes can lead to variations in gender development. When this affects gender assignment and sexual organ development, the child is said to have a disorder of sexual development, or DSD. These conditions can cause a person’s genitalia to look like one gender, even as the baby possesses the internal sexual organs of another gender.

There are various words used to describe this condition, such as intersex, hermaphrodite, or pseudohermaphroditism, but the preferred term is DSD, according to the University of Michigan Health System and family advocacy groups that represent DSD children.

While multiple DSD types exist, they are typically divided into four categories:

1. 46, XX Intersex — XX intersex occurs when a person has external genitalia that resemble a male’s, yet has ovaries and the XX chromosomes of a woman. 

The most common cause is congenital adrenal hyperplasia, which occurs when the adrenal glands don’t produce enough of the hormones cortisol and aldosterone and overproduce testosterone.

2. 46, XY Intersex — A person has male chromosomes, but the genitalia may appear ambiguous or distinctly female. 

Any condition that affects ovary/testicle formation, testosterone formation, or the body’s ability to use testosterone can cause XY intersex. Examples of these conditions include XY pure gonadal dysgenesis, some types of congenital adrenal hyperplasia, 5-alpha-reductase deficiency, or androgen insensitivity syndrome (AIS).

3. True Gonadal Intersex — Formerly known as true hermaphroditism, this condition occurs when a person has both ovarian and testicular tissue. Their chromosomes can be XX, XY, or both sets of chromosomes. The genitalia can appear distinctly male, distinctly female, or be ambiguous. 

Causes for this condition are largely unknown. One theory is that exposure to agricultural pesticides causes the condition.

4. Undetermined or Complex Intersex — These conditions occur when a person has extra chromosomes or only one X chromosome. While the result may not be differences in internal and external genitalia, people with these conditions can have other sexual disorders, such as affected sex hormone levels and impacted sexual development. 

Conditions can include Klinefelter syndrome (XXY chromosome pattern) or Turner syndrome (X chromosome only).

Children with DSD may display abnormalities at birth or may develop hormone-related symptoms later that indicate an underlying condition.

Treatments for these conditions are often controversial.  In some instances, the parents are asked at birth or shortly thereafter to assign a particular sex to a baby. As an infant, the child may have undergone surgeries to make the sexual organs appear more male or female. However, some parents believe in waiting until a child grows older and identifies with a particular gender. Parents and a team of medical professionals typically collaborate to consider the child’s condition(s) and try to determine the best approaches.

Reviewed by Dr. Sara Connolly, April 2019