Mixed gonadal dysgenesis (MGD) is a condition that affects how the body grows and develops before birth and at puberty.

People with MGD have gonads that may not develop fully, and they may not make typical amounts of hormones.

Before birth, people with MGD’s bodies may develop features typical of a girl, a boy, or both a girl and a boy.

What makes a person’s body develop as a boy or a girl?

There are many factors that are important for how the body develops. These include genetics and hormones. Genetics are instruction codes and hormones are chemical messengers. In terms of genetics, babies are usually born with a total of 46 chromosomes. Two of the chromosomes guide how the reproductive parts grow. They are called the “sex chromosomes.” Girls usually have two X chromosomes (46,XX). Boys usually have one X and one Y chromosome (46,XY). Before a baby is born, these chromosomes guide how the gonads develop. Gonads are glands that make the “sex hormones” estrogen and testosterone. 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, at puberty, hormones make the body change again.

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, girl / woman, 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 different pattern of chromosomes in different cells. This is called “mosaicism.” In mosaicism, some cells have one pattern and other cells have a different pattern. When this happens to sex chromosomes, this is called “sex chromosome mosaicism.” In people with MGD, some cells have a 46,XY pattern. Other cells have a 45,X pattern. The 45,X means some cells have lost one of the sex chromosomes. There may be other combinations of chromosome patterns too.

Because of this, people with MGD have gonads that develop on a less typical path. The gonads are sometimes underdeveloped. Underdeveloped gonads are called “dysgenetic” or “streak” gonads. These gonads may not make sex hormones before birth. Other times, one or both of the gonads may have some testis tissue and / or ovary tissue. These gonads may make some sex hormones.

Depending on what hormones and how much of the hormones are made, people with MGD are born with reproductive parts that may be typical for a girl, a boy, or both.

How do the reproductive parts develop in people with mixed gonadal dysgenesis?

People with MGD have reproductive parts that may develop along a male or female path. Some signs of MGD may be:

  • Genitals: The penis may be small. The clitoris may be large. The genitals may have features of both a boy and a girl.
  • Gonads: There may be a typical gonad on one side and an underdeveloped (“streak”) gonad on the other side.
  • Vagina: Some people with MGD may have a small vagina. Some may have a urogenital sinus. TA urogenital sinus is when the vagina and the tube carrying urine join up inside the body. Instead of having two holes on the outside of the body, there is just one.
  • Womb or uterus: A uterus may or not be present.
  • Puberty: Changes in the body at puberty depend on what hormones are made, and how much are made. If the gonads make testosterone at puberty, there may be growth of the genitals, deepening of the voice, and growth of 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 a testicle in the groin instead of the scrotum. This is called an undescended testicle. The doctor will not be able to feel an underdeveloped, “streak” gonad. The doctor can not feel this far inside the body. The genitals may not look typical for a boy or a girl.

Testing will need to be done to learn and make a 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 which hormones the gonads are making and how much.
  • Pelvic ultrasound – This is an imaging test that looks for gonads inside the body 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, ethics, social work and child life. We partner with patients and families to make a personal treatment plan based on each patient’s needs. Our team will talk about treatment options. We help patients and families make informed decisions for their child’s ongoing care. We provide emotional and psychological support. We want patients and families have their best quality of life. We try to let patients and families know what to expect. We provide resources to help with the road ahead.

Medical Care

Children with MGD need routine checks to monitor their growth and development, and their overall health. They may need tests to check their hormone levels and for other health issues (for example, vision, hearing, kidneys and heart). Children with MGD may need treatment with hormones at puberty. Hormones at puberty make changes in the body. Treatment with estrogen causes breast and sexual development, overall growth and strong bones. Treatment with testosterone causes growth of the penis, deepening of the voice and increased facial hair.

Surgical Care

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 later to prevent future cancer. If a child has an undescended testicle, it may need to be moved down into the scrotum. Questions about additional surgeries can be discussed with the medical team as needed.

Psychosocial Care

MGD is a lifelong condition. Having a lifelong condition can affect a person’s sense of well-being. It can also cause stress to family members. Our psychologist and social worker, together with our team, help patients and families identify and address concern. We help families think about how to share information with loved ones about the diagnosis. We also help them 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.