Intersex conditions, also known as disorders of sex development (DSD), occur when infants are born with a mix of male and female genitalia. The disorders cause a mismatch in the external and internal reproductive organs. The child's body may not be completely male, nor totally female. For example, a person may appear female, but have male (XY) chromosomes and testicles; or a person may have female internal organs such as ovaries and a uterus, but have a clitoris that is enlarged to resemble a penis.
Causes and Types of Intersex Conditions
In some children, the exact cause of their intersex condition may not be known, but in others the defect lies within the chromosomes, gonads, or anatomical sex. Frequency of these conditions depends upon the specific type. The most common cause of intersex conditions is congenital adrenal hyperplasia (CAH), which occurs in 1 out of every 15,000 live births worldwide. There are four main categories of intersex conditions:
Female with male-looking or ambiguous genitals
In this type of intersex condition, a person has female (XX) chromosomes with normal ovaries and uterus, but the external genitals appear to be male. The clitoris may be enlarged and look like a penis. The folds of skin of the external female genitals (“lips,” or labia) may also be joined together to close the vagina.
This condition is called 46, XX DSD or 46, XX with virilization. It usually results from a female fetus being exposed to a large amount of male sex hormones before birth, such as:
- Congenital adrenal hyperplasia (the most common cause) is a group of inherited disorders in which the adrenal gland lacks an enzyme that is needed to make the hormones cortisol and aldosterone. As a consequence, the body produces more androgens (male sex hormones).
- Exposure by the mother to male hormones during pregnancy, such as testosterone gel used by men to treat a hormone deficiency.
- Tumors in the mother that produce male hormones (often ovarian tumors)
- Deficiency in the enzyme aromatase, which is responsible for converting male hormones to female hormones. In this case, symptoms may not appear until puberty.
Male with female-looking genitals
With this type of intersex condition, a person has male chromosomes (XY), but the external genitals appear female, ambiguous, or incompletely formed. In some cases, the testes do not descend and remain inside the body. This is known as 46, XY DSD or 46, XY with undervirilization.
In order for male external genitals to develop, the body requires a balance between the female and male sex hormones. A shortage of male hormones can lead to 46, XY DSD. This may occur as a result of:
- Testes problems which result in too little male hormones (such as low testosterone) being produced.
- Testosterone formation problems, such as a shortage of an enzyme required for one of the steps during the production of this male sex hormone.
- Difficulty using testosterone, in which the body makes enough of the hormone, but it can’t use it properly. This can occur when the person lacks an enzyme needed to convert testosterone into another active form, or when cells in the body don’t respond appropriately to testosterone (androgen insensitivity syndrome).
A mix of male and female characteristics
In this type of intersex condition—known as true gonadal DSD or ovotesticular DSD—the person has both testicular and ovarian tissue. The tissue may appear as a separate ovary and testis, or show up within the same gonad (called an ovotestis).
The external genitals can appear as male, female, or ambiguous. For most people, the underlying cause of true gonadal DSD is unknown, although some studies in animals have linked this condition to exposure to pesticides used for agriculture.
Complex or undetermined DSD
Other problems with the chromosomes can lead to intersex conditions. In some cases, a person has an extra sex chromosome—either an X or a Y—as is the case with 47, XXY or 47, XXX. This condition also occurs when one of the X chromosomes is missing (45, XO).
Unlike other types of intersex conditions, these disorders don’t lead to a mismatch between the internal and external genitalia. However, there may be other problems, such as with sexual development at puberty or the levels of the sex hormones.
Signs of an Intersex Condition
Signs of an intersex condition depend upon the underlying cause, but may include:
- Genitals that are ambiguous at birth
- Unusually small penis (micropenis)
- Enlarged clitoris (clitoromegaly)
- Partial fusion of the labia
- Testes that appear to be undescended (in boys), but may be ovaries
- Masses in the labia or groin (in girls) that may be testes
- Opening of the urethra is somewhere other than the tip of the penis in boys, or above the vaginal opening in girls (hypospadias)
- Genitalia that appear unusual at birth
- Abnormalities in the electrolyte levels in the blood due to the inability of the adrenal gland to make aldosterone, a steroid hormone produced by the outer layer of the adrenal cortex
- Absent or delayed puberty
- Unexpected changes during puberty
Diagnosing Intersex Conditions
While signs of intersex conditions may be more physically prominent in some and can lead to early diagnosis, in others, indicators are not as clear, causing some of the associated conditions to be identified in late childhood or adolescence when the sexual organs are further along in their development and hormone production increases.
To diagnose an intersex condition, a detailed family history may reveal past accounts of intersex disorders. For this, a physician will typically begin by taking this history and prenatal history, followed by a physical examination of the child's anatomy. If an intersex condition is suspected, blood tests may be performed to check hormone levels, and genetic studies may be conducted to determine if chromosomal abnormalities are present. By taking a sample of amniotic fluid, blood, or bone marrow, chromosomes can be counted and examined for structural changes.
Imaging studies, such as a pelvic ultrasound, can generate views of both the male and female reproductive organs, revealing key information about the sex of the child. They, along with endoscopic examination, may also determine whether the internal sex organs are absent, such may be the case with undescended testicles.
Treatment for Intersex Conditions
Treatment for intersex conditions depends upon the underlying cause, but may include medication or surgery. Health professionals often recommend delaying surgery until the child is old enough to take part in decisions about treatment.
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