What Makes a Person’s Body Develop as a Boy or a Girl?
How the body develops depends on genetics and hormones. Generally, babies are usually born with a total of 46 chromosomes. Girls usually have two X chromosomes (46,XX). Boys usually have one X and one Y chromosome (46,XY). When a baby is in the womb, these chromosome patterns guide how the gonads develop. Gonads are glands that make hormones like estrogen and testosterone (known as “sex hormones”). Most of the time, girls’ gonads develop into ovaries, and boys’ gonads develop into testicles. Ovaries make estrogen and some testosterone. Testicles make testosterone. Before birth, testosterone usually makes the body develop as a boy. People whose bodies do not make large amounts of testosterone develop as a girl. Later, hormones make the body change at puberty.
How a person’s body grows and develops (their “sex”) is not the same as their “gender.” “Gender is about a person’s sense of self. It is about their inner feeling of being a boy / man or girl / woman, or both, or neither.
Learn more about Gender and Sex: What Makes a Person a Boy or a Girl?
What Causes Mixed Gonadal Dysgenesis?
People with MGD have a mixed pattern of chromosomes. This is called “mosaicism.” In mosaicism, some cells have one pattern and other cells have a different pattern. In MGD, some cells have a 46,XY pattern. Other cells have a 45,X pattern. This means some cells have lost one of the sex chromosomes. There may be other combinations of chromosome patterns too.
Because of this, babies with MGD have gonads that do not develop in the typical way. The gonads are sometimes underdeveloped. Underdeveloped gonads are called “dysgenetic” or “streak” gonads. These gonads may not work or make sex hormones before birth. One or both gonads may also have testis tissue and / or ovary tissue. These gonads may make some hormones.
Depending on what hormones and how much or little are made, babies with MGD are born with genitals that may have typical features of a girl, or a boy, or a mixture of features.
What Are the Characteristics of Mixed Gonadal Dysgenesis?
Children with MGD can be boys or girls. Some signs of MGD may be:
- Genitals: The penis may be small in some boys. The clitoris may be large in some girls. The genitals may have features of a boy and a girl.
- Gonads: There may be a gonad on one side and an underdeveloped (“streak”) gonad on the other side. The streak gonad is inside the body.
- Vagina: Some girls may have a small vagina. Some may have a urogenital sinus. This means the vagina and the tube carrying urine join up inside the body instead of having two holes that can be seen from outside the body.
- Womb or uterus: Girls usually have a uterus. Boys usually do not.
- Puberty: Changes in the body in boys and girls at puberty depend on what hormones are made, and how much or little. If the gonads make testosterone at puberty, there may be growth of the genitals, deep voice and facial hair.
How Is Mixed Gonadal Dysgenesis Diagnosed?
MGD is often diagnosed by a medical exam and testing at birth. During an exam, the doctor may feel an undescended testicle in the groin. The doctor will not be able to feel an underdeveloped, “streak” gonad inside the body. The genitals may not look typical for a boy or a girl.
Testing will need to be done for a complete diagnosis. Testing may include:
- Karyotype – This is a blood test that looks at a person’s chromosomes, including the X and Y chromosomes. This may show if there is a mixed pattern of chromosomes.
- Hormone levels – This is a blood test to check what hormones the gonads are making and how much.
- Pelvic ultrasound – This is an imaging test that looks for the gonads and for a uterus.
- Laparoscopy – This is a surgery using a small camera. The surgeon looks for the reproductive parts inside the body. The surgeon may also take small pieces of tissue (called a biopsy) for testing.
How Do We Care for People with Mixed Gonadal Dysgenesis?
We care for people with MGD as a team of specialists working together. Our team has specialists in endocrinology, gynecology, urology, psychology, genetics and ethics. We work with patients and families to make a personal treatment plan based on each patient’s needs. Our team will talk about treatment options and help patients and families make informed decisions for their / their child’s ongoing care. We will provide emotional and psychological support to help patients and families have the best quality of life. We try to let patients and families know what to expect and provide resources to help with the challenges ahead.
Having a chronic condition such as MGD can affect a person’s sense of well-being and can cause stress to family members. Our psychologist and social worker help patients and families identify and address areas of concern. We help families think about how to share information with loved ones about the diagnosis and how to find community resources. Our psychologist meets with children from a young age, through adulthood. Our goal is to ensure they develop a healthy sense of self and feel comfortable with their gender. Also, the psychologist will address any mental health concerns that may be present.
Children with MGD need routine checks to monitor their growth and development, and their overall health. They may need blood tests to check their hormone levels. Girls with MGD may need treatment with estrogen at puberty. Treatment with estrogen will promote breast and sexual development, overall growth and strong bones. Boys with MGD may or may not need hormone treatment, depending on if they make enough testosterone.
Most children with MGD do not need surgery at birth for medical reasons. If a child has an underdeveloped, streak gonad, it may need to be removed to prevent future cancer. If a boy has an undescended testicle, it may need to be moved down into the scrotum. The need for additional surgeries can be discussed with the medical team as needed.