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Beyond Just XX or XY: The Complexities of Biological Sex

One of the reasons human biology is so interesting is because it’s so complex; rarely are there neat answers. We’re often taught that when it comes to biological sex, everything fits into two boxes: XY and XX. However, it turns out that, just like the rest of biology, things are a little more complicated than that. Some people not have chromosomes or sexual characteristics that neatly fit into those two boxes. These people have disorders of sex development (DSDs), also known as differences of sex development or intersex conditions. Due to the taboo nature of the subject and differing opinions of what qualifies as a DSD, it's hard to pin down exactly how many people have DSDs—estimations have…

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 Imane Khelif and The Burden of Suffering

The fact is that athletes with certain DSDs will have significant advantages so long as they’re competing against biological females, but the flip side of their DSD is that their testosterone levels might be significantly higher than a females and lower than that of an elite male athlete. As a result, to deny them access to the women’s category is effectively ask them to compete in a category where they not only lose their competitive advantage, enter with a significant disadvantage.

 Management guidelines for disorders/different sex development (DSD)

Disorders of sex development (DSD) include a wide range of anomalies among the chromosomal, gonadal, and phenotypic (genital) characteristics that define sexual differentiation. At present, a definition as Different sexual development (DSD) is currently preferred.

 More women than expected are born with a hidden variation in sex development

It is often assumed that women have XX chromosomes and men have XY, but biology is more complex. Some women have XY chromosomes — a natural variation in sex development. They grow up identifying and living as women, and most only discover well into puberty that they are different. Danish researchers have, for the first time, mapped how many women have XY chromosomes. The proportion was higher than expected.

 The Approach to Patients with Disorders of Sex Development (DSD) in the Era of Precision Medicine: The Careful Use of Terminology

The term “DSD” was coined for “disorders of sex development”, referring to conditions where the chromosomal, gonadal and/or genital sex is discordant or ambiguous, to replace terms considered imprecise and stigmatizing. Recently, the term “disorder” has been questioned and the term “differences” has been proposed as not stigmatizing, reflecting that the term DSD should be depathologized.

Articles of Interest

Algerian Olympic Boxer Imane Khelif Admits To Having Male Sex Chromosome For The First Time

Despite the admission by Khelif’s coach and the repeat medical record leaks confirming Khelif was biologically male, mainstream media outlets and activists continued to insist that Khelif was female and had simply been the victim of a “transphobic smear campaign” which targeted him because of his appearance.

Ambiguous genitals? You may have wrinkly genes

The proper development of testes and ovaries is driven by a tightly regulated network of genes and regulatory factors. Misregulation of this network in humans results in atypical development of chromosomal, gonadal or anatomical sex, resulting in so-called disorders of sex development (DSDs). The “umbrella” term DSD includes a variety of different disorders, from relatively mild, such as hypospadias (abnormally placed opening of the urethra) to complete sex reversal where, for instance, XY individuals develop as females.

Boy, girl or …? Dilemmas when sex development goes awry

It’s impossible to lump this spectrum of conditions into a single category. The term intersex, for instance, describes those with ambiguous genitals, or gonads with both testis and ovarian tissue. But it doesn’t apply to others, such as XY girls with androgen insensitivity. Disorders of sex development (DSD) is the term adopted medically. Not surprisingly, patients quail at labels like this that denote a disease and invite discrimination

Differences of Sex Development 101: it’s complicated

Intersex is an umbrella term for people whose reproductive organs, sexual anatomy or chromosome patterns differ from the biological definition of male or female. We call these conditions Differences of Sex Development, or DSDs.

Differences of sexual development and their clinical implications

The term ‘differences of sex development’ (DSD) defines a wide spectrum of conditions in which the development of chromosomal, gonadal or anatomical sex is atypical. Presenting at birth or puberty, or as primary subfertility, the precise diagnosis is difficult, the clinical management is controversial and multidisciplinary team care is imperative.

Differences/Disorders of Sex Development: Medical Conditions at the Intersection of Sex and Gender

Defined as congenital conditions in which development of chromosomal, gonadal, or anatomic sex is atypical, differences or disorders of sex development (DSDs) comprise many discrete diagnoses ranging from those associated with few phenotypic differences between affected and unaffected individuals to those where questions arise regarding gender of rearing, gonadal tumor risk, genital surgery, and fertility.

Disorders of Sex Development

Disorders of sexual development (DSD) encompass a group of congenital conditions associated with atypical development of internal and external genital structures. These conditions can be associated with variations in genes, developmental programming, and hormones. Affected individuals may be recognized at birth due to ambiguity of the external genitalia. Others may present later with postnatal virilization, delayed/absent puberty, or infertility.

Disorders of Sex Development (DSDs): An Update

With the advent of the robust new technologies of array comparative genomic hybridization and genomic sequencing in recent years, many new sex-determining genes have been identified.

Disorders of Sex Development: Challenges for the Future

The perpetual challenge in the diagnosis and management of patients with disorders of sex development (DSD), to paraphrase the adage, is that as our circle of knowledge in the genetic mechanisms of DSD expands, so does the circumference of darkness surrounding it. New technologies (comparative genomic hybridization, sequencing by hybridization, and next generation sequencing) are rapidly generating massive amounts of information on the pathogenesis of DSD.

Disorders of Sexual Development: Current Status and Progress in the Diagnostic Approach

Disorders of sexual development (DSD) are conditions with an atypical chromosomal, gonadal or phenotypic sex, which leads to differences in the development of the urogenital tract and different clinical phenotypes. Some genes have been implicated in the sex development during gonadal and functional differentiation where the maintenance of the somatic sex of the gonad as either male or female is achieved by suppression of the alternate route.

Explaining Disorders of Sex Development & Intersexuality

Explaining-Disorders-of-Sex-Development-Intersexuality.aspxA DSD is a mismatch between a child's chromosomes, or genetic material, and the appearance of the child's genitals. A child may present with a DSD in infancy, childhood or adolescence. Previously, DSDs were called "intersex" conditions. This means "between the sexes." However, this term felt uncomfortable to some people with who identified themselves as strongly male or strongly female. Note: Most people with a DSD prefer the term "Difference" of Sex Development rather than "Disorder," because the word "disorder" implies that there is something "wrong" with the person rather than a natural variation.

One in 500 men carry extra sex chromosome, research suggests

While most men have one X and one Y chromosome, some are born XXY or XYY, putting them at increased risk of health issues ranging from type 2 diabetes, blocked blood vessels and chronic obstructive pulmonary disease (COPD), a lung condition, the study found.

Sex tests brought in after data showed 50-60 DSD athletes in finals, World Athletics says

Sex tests brought in after data showed 50-60 DSD athletes in finals, World Athletics says This article is more than 4 months old Cheek swabs introduced for world championships Data presented at scientific panel in Tokyo on Friday Sean Ingle in Tokyo Fri 19 Sep 2025 09.00 EDT Share Between 50 and 60 athletes who went through male puberty have been finalists in the female category in global and continental track and field championships since 2000, according to a senior World Athletics official. World Athletics has introduced SRY screening, a gene test that uses a cheek swab to assess if someone is biologically male or female, for the world championships in Tokyo.

What are DSDs? And why is everyone talking about them at the Paris 2024 Olympics?

There's a lot of controversy online right now surrounding Olympic boxer Imane Khelif, who was reportedly born with DSDs, or differences in sexual development.

What is intersex? This is intersex!

Intersex is not the same as DSD (disorders/differences of sex development), yet both terms refer to the same group of people. Sometimes DSD and intersex do speak on the same issues. However, DSD and intersex have a substantially different approach. Intersex and DSD can be seen as the different sides of the same coin.

Resources

Association for X and Y Chromosome Variations

AXYS, the Association for X and Y Chromosome Variations, is an advocacy, education and support organization for individuals with X and Y chromosome variations and their families. This includes those with Klinefelter syndrome (47,XXY), Trisomy X (47,XXX), 47,XYY, 48,XXYY, 48,XXXY and related genetic conditions.

The Focus Foundation

The Focus Foundation is dedicated to helping children and families affected by X & Y Variations, Dyslexia, and/or Developmental Dyspraxia. The Focus Foundation believes that through increased awareness, early identification and syndrome-specific treatment, children with these conditions can reach their full potential.