Disorders of sexual development (DSDs) are conditions that lead to atypical sexual development in an infant. These conditions are also referred to as differences of sexual development or disorders of sexual differentiation.

Some infants with disorders of sexual development may be completely healthy, other than having genitals that appear different from those of other infants. Others may have more significant health problems related to the same processes that led to their sexual development to differ from expectations.

In cases where infants have ambiguous genitalia that appear somewhere between stereotypical male and female, DSDs can make it difficult to assign a sex at the time of birth. DSDs used to be known as intersex conditions because affected infants appeared to be between (inter-) the sexes.

Sexual Development Basics

Schools often teach that sex is determined by the sex chromosomes. People with two X chromosomes are female. People with an X chromosome and a Y chromosome are male.

However, sexual development is not quite that simple. A number of different factors determine whether an infant develops as male or female. Although in general an XX person is female and an XY person male, there are exceptions. There are also individuals who have other combinations of sex chromosomes, such as X(alone) or XXY.

Understanding the basics of sexual development makes it easier to understand disorders of sexual development. In humans, the reproductive organs develop from two sets of ducts—Mullerian (M) ducts and Wolffian (W) ducts. What happens next depends on the signals produced in the body. Depending on what hormones are made, and which hormones are responded to, one of those sets of ducts regresses and the other develops.

Stereotypical male development occurs in response to the hormones anti-Mullerian hormone (AMH), testosterone, and dihydrotestosterone (DHT). AMH causes the regression of the M ducts. Testosterone causes the testicles to descend and stimulates the development of internal structures such as the epididymis. Stereotypical female development is caused by the absence of testosterone and AMH. The W ducts regress and the M ducts turn into the uterus, fallopian tubes, and upper vagina.

The basic structures of the external genitalia are the same in both male and female fetuses, early in development. Their appearance at the time of birth is dependent on the presence or absence of DHT. Genital structures that come from the same source tissues are known as homologous structures.

DSD Symptoms

There are a number of different types of conditions that fall under the category of disorders of sexual development. These conditions can be categorized by either their symptoms or their causes. Types of DSD symptoms include:

  • Labioscrotal swelling fuses to become the scrotum

  • Genital tubercle becomes the glans (head) of the penis

  • Genital folds fuse around the urethra to become the shaft of the penis

  • Two sides of the labioscrotal swelling become the labia majora

  • Genital tubercle becomes the clitoris

  • Genital folds become the labia minora

  • Atypical external genitaliaAtypical internal genitaliaCombined differences in external and internal genitalia

The presence of a DSD is not always clear at the time of birth. For example, an infant with complete androgen insensitivity syndrome may appear to be a typical female, even though they have testes instead of ovaries. Parents of young girls born with MRKH syndrome may not notice their infant lacks a vagina or uterus. For differences of sexual differentiation that do not become clear until puberty, possible symptoms include:

  • Failure to begin menstruationSudden penile growthInfertility or decreased fertility

Causes

There are several different types of situations that can lead to an infant developing a DSD. These include:

Having an Abnormal Number of Sex Chromosomes

There are several ways that a person can have an abnormal number of sex chromosomes. The most common variations are a single X chromosome, written XO (or 45,X), or an extra X chromosome alongside a Y chromosome—XXY (or 47,XXY).

Girls with a single X chromosome are said to have Turner Syndrome. They are usually shorter than average and have problems with fertility. Boys born with an extra X chromosome are said to have Klinefelter syndrome. They tend to be taller than average. They also have reduced fertility, less body hair, and may be infertile.

Having a Gene Mutation That Affects Hormone Production

One of the more well-known DSDs caused by mutations that affect hormone production is Congenital Adrenal Hyperplasia or CAH. Girls with CAH have two X chromosomes, but they produce too much testosterone. This can cause them to be born with a clitoris that resembles a penis. Boys with CAH have normal-appearing genitalia.

In both sexes, individuals with CAH may be shorter than average, develop pubic hair early, and undergo early puberty. Although people with CAH can have long, healthy lives, their health must be carefully managed. They may be at risk for what is known as an adrenal crisis due to the fact that their bodies do not produce cortisol.

Another condition related to hormone production is 5-alpha reductase deficiency. This is a condition that affects male sexual development. 5-alpha reductase is the primary enzyme that turns testosterone into DHT during early development. XY individuals with 5-alpha reductase deficiency may be born with genitalia that appear to be female. They may also have more male-appearing genitalia that are small.

Interestingly, at puberty, there are other pathways through which the body can make DHT. This means that the penis and the scrotum will grow larger, they’ll develop pubic hair, and they may gain some muscle mass. Depending on the appearance of the genitals at the time of birth, babies with 5-alpha reductase deficiency may be raised as male or female. Some individuals raised as female develop a male gender identity during or after puberty.

Having a Gene Mutation That Makes the Body Less Able, or Unable, to Respond to Hormones

The body responds to hormones through their interactions with hormone receptors. These receptors allow the hormones to interact with cells. It is through this interaction that hormone effects occur.

In XY individuals with androgen insensitivity syndrome, their bodies make normal amounts of testosterone and DHT. However, their cells can’t respond to it. Or, in the case of partial androgen insensitivity syndrome, they respond at a lower level. This means that these individuals’ bodies and brains tend to develop as female, at least in the most complete form of the condition.

Being Exposed to External Hormones During Important Phases of Development

Sometimes a baby is exposed to unusual levels of hormones while it is developing in the womb. This could be, for example, because the child’s mother has a tumor that produces an excess of testosterone. It could also be because of exposure to chemicals that alter the hormonal environment.

Diagnosis

The diagnosis of DSDs varies based on the causes and symptoms of the condition. If a baby is born with visibly ambiguous genitalia, testing is indicated. This could include chromosomal testing and tests to determine the relative levels of hormones in the baby’s blood. It might also include imaging to look for the presence of testes, ovaries, and other internal structures.

When a child appears to be healthy at the time of birth, with no obvious differences in genitalia, DSDs may not be diagnosed for quite some time. Some conditions may not be detected until puberty. If a girl doesn’t menstruate or a boy doesn’t develop as expected, this could be a reason for doctors to start looking for a cause.

Through testing similar to that mentioned above, they may detect the presence of a DSD. Other individuals with differences in sexual development may not discover the condition until they’re an adult struggling with infertility or other late-onset symptoms.

Treatment

Many children with differences of sexual development do not need any treatment. They will grow up to be happy, healthy children and adults. Other children may need hormone treatments at various phases during their life to ensure healthy growth and development.

Still, others may require surgery to address changes in the reproductive organs that affect function. It is recommended that some children with DSDs have their ovaries or testes removed if they have a condition where there is thought to be an increased risk of cancer. Teens and adults with DSDs may also benefit from counseling to deal with infertility and other reproductive health problems.

Gender Identity and DSD

Historically, infants with disorders of sexual development were often surgically “assigned” a sex during infancy that would allow the child to have the most aesthetically acceptable genitalia. It was thought that people’s gender identity was almost entirely determined by how they were raised.

However, in recent years there has been a growing understanding that gender identity is affected by biological and environmental factors that may be present even before birth. Therefore, doctors take many more factors into consideration when suggesting a sex of rearing for an infant with a difference of sexual development.

Surgical modification of infant genitalia is also becoming less routine in cases where the function is not affected. For example, a young girl with an enlarged clitoris that resembles a penis does not have functional concerns. A young boy with a blocked urethra does.

Some doctors still recommend cosmetic genital surgery for young children with ambiguous genitalia to manage parents’ discomfort and help them bond with their children. However, the evidence is unclear as to the effects of such surgeries on the child—both in terms of emotional health and sexual function.

As such, parents should consider consulting multiple experts from different fields before deciding whether they are going to pursue cosmetic genital surgery in an infant with a DSD.

A Word From Verywell

Coping with disorders of sexual differentiation is often more of a challenge for infants’ parents rather than the affected infants themselves. When a baby is born with differences of sexual development, it can be very stressful for parents.

One of the first questions that many parents are asked about their child is, “Is it a boy or a girl?” When you don’t have an easy answer to that question, every interaction can seem fraught with tension.

However, before parents rush into making decisions that can permanently alter their children’s lives, it’s important to take a breath. In most cases, DSDs are not an emergency. Sometimes, the child has no significant health problems at all. Their genitals may appear different than other children, but they are happy, healthy, and able to function.

Other times, they may need one or more surgeries to deal with problems such as hypospadias. These decisions are hard to make, so it’s important to ask for support. Talking to experts, doctors, and therapists can help you make the best choices for your child and your family. That’s not something you want to rush.