DSD stands for differences of sex development (sometimes called disorders of sex development). It refers to a group of conditions where a person’s external anatomy, internal reproductive organs, or chromosomes don’t follow the typical patterns of male or female development. The older term for these conditions is “intersex,” which is still widely used outside of medical settings.
What DSD Actually Means Biologically
During fetal development, sex characteristics normally follow a coordinated path: chromosomes guide hormone production, hormones shape internal organs, and internal organs influence external anatomy. In DSD, one or more steps in that chain diverge from the expected pattern. Someone might have XY chromosomes but develop external anatomy that looks female, or XX chromosomes with some typically male physical features. The mismatch can occur at the chromosomal, hormonal, or anatomical level.
A nationwide Scottish study found that about 1 in 1,881 newborns have noticeably atypical genitalia at birth. In most of those cases, sex assignment wasn’t delayed, but roughly 1 in 11,000 births involved enough ambiguity that assigning sex at birth required further evaluation. Many milder forms of DSD aren’t detected until puberty or even adulthood, so the true prevalence is higher than what’s caught at birth.
Common Types of DSD
Congenital Adrenal Hyperplasia (CAH)
CAH is one of the most common causes of DSD. The adrenal glands, which sit above the kidneys, normally produce cortisol (the stress-response hormone), aldosterone (which regulates sodium and potassium), and androgens like testosterone. In CAH, a genetic change knocks out one of the enzymes needed to make these hormones. The body compensates by overproducing androgens, which can cause a baby with XX chromosomes to be born with genitalia that look more typically male.
The more serious “classic” form can also create a dangerous shortage of cortisol and aldosterone, leading to problems with blood pressure, blood sugar, and electrolyte balance. A milder “nonclassic” form may not show up until childhood or adolescence, when it can trigger early puberty, rapid growth, severe acne, or irregular periods.
Androgen Insensitivity Syndrome (AIS)
AIS occurs when the body’s cells can’t respond to androgens, even though the body produces them. It’s caused by a change in the gene that builds androgen receptors. In the complete form, a person with XY chromosomes develops external anatomy that looks entirely female, and the condition often isn’t discovered until puberty when menstruation doesn’t start. In the partial form, the body responds to some androgens but not all, resulting in a range of physical outcomes from typically female to typically male, with many variations in between.
Klinefelter Syndrome
Klinefelter syndrome involves an extra X chromosome, giving a person a 47,XXY pattern instead of the typical 46,XY. It affects about 1 in 650 male newborns, making it one of the most common chromosome-related conditions. Up to 65 percent of people with Klinefelter syndrome are never diagnosed.
The extra chromosome leads to smaller testes and lower testosterone production. Without treatment, this can cause delayed puberty, breast tissue growth, reduced muscle mass, lower bone density, less facial and body hair, and fatigue. People with Klinefelter syndrome are typically 2 to 3 inches taller than expected for their family. Children may experience mild delays in speech, an increased risk of learning disabilities (particularly with reading and writing), and higher rates of ADHD and anxiety. Up to half of those affected can still have biological children through assisted reproduction.
Other Chromosomal Variations
Some forms of DSD involve a different kind of chromosomal mismatch. In 46,XX testicular DSD, a person has typical female chromosomes but develops male physical characteristics. In about 80 percent of these cases, a key gene called SRY (which normally sits on the Y chromosome and triggers male development) has been accidentally transferred to another chromosome. The remaining 20 percent develop male characteristics through a different, less understood mechanism.
How DSD Is Identified
When a newborn’s anatomy doesn’t clearly fit male or female categories, doctors begin a series of tests. The first step is a chromosome analysis to determine the underlying genetic pattern. Hormone levels are measured in the first few days and weeks of life, though timing matters: some hormones are naturally elevated right after delivery due to birth stress and aren’t reliable until day three or four.
An ultrasound of the pelvis and urinary tract helps map the internal anatomy, including whether a uterus, ovaries, or testes are present and where they’re located. More advanced genetic testing, such as sequencing that scans for small deletions or duplications in DNA, is used when initial tests don’t provide a clear answer. In some cases, additional imaging or a small camera procedure helps surgeons understand the internal anatomy before any decisions are made.
How DSD Is Managed
Current medical guidelines emphasize that DSD care should involve a team of specialists working closely with the family over the long term. That team typically includes endocrinologists, geneticists, urologists, gynecologists, and psychologists. The goal is to address the full range of needs: physical health, hormone balance, psychological wellbeing, fertility, and social support.
Children with DSD are encouraged to participate in decisions about their own care as they grow older. Families are also encouraged to connect with advocacy groups, which can offer perspectives that medical teams alone may not provide. Treatment plans vary widely depending on the specific condition. Some people need lifelong hormone replacement, while others need no medical intervention at all. For conditions like classic CAH, managing cortisol and aldosterone levels is essential to prevent a potentially dangerous adrenal crisis.
The Surgery Debate
One of the most contested issues in DSD care is whether and when to perform genital surgery on infants or young children who can’t yet consent. The European Society for Paediatric Urology’s consensus statement holds that blanket bans on surgery are just as harmful as requiring surgery for everyone. Their position is that each child’s situation is unique, and that families, working alongside expert teams, should weigh the pros and cons of all options: observation, hormone therapy, or surgery.
Critics of early surgery argue that irreversible procedures should wait until the person can make their own informed choice. Supporters argue that some interventions are medically necessary and that delaying can carry its own physical and psychological costs. This remains an active and deeply personal area of debate, with no single answer that fits every family or every condition.