The appearance of XX males can fall into one of three categories: 1) males that have normal internal and external genitalia, 2) males with external ambiguities, and 3) males that have both internal and external genital ambiguities (true hermaphrodites). External genital ambiguities can include hypospadias, micropenis, and clitoromegaly. On average, the appearance of XX males differs from that of an XY male in that they are smaller in height and weight. Most XX males have small testes, are sterile, and have an increase in maldescended testicles compared to XY males. Some XX male individuals have decreased amounts of body hair and decreased libido. Individuals with this condition sometimes have feminine characteristics, with varying degrees of gynecomastia but with no intra-abdominal Müllerian tissue. According to research at the University of Oklahoma health science centers, despite XX males exhibiting feminine characteristics, their behaviours are usually representative of masculinity in their culture.

People with 46,XX testicular DSD have male external genitalia. They generally have small testes and may also have abnormalities such as undescended testes (cryptorchidism) or the urethra opening on the underside of the penis (hypospadias). A small number of affected people have external genitalia that do not look clearly male or clearly female (ambiguous genitalia). Affected children are typically raised as males and are likely to have a male gender identity.

A supplemental system of phenotypic grading that uses seven classes instead of the traditional three was proposed by pediatric endocrinologist Charmian A. Quigley et al. in 1995. The first six grades of the scale, grades 1 through 6, are differentiated by the degree of genital masculinization; grade 1 is indicated when the external genitalia is fully masculinized, grade 6 is indicated when the external genitalia is fully feminized, and grades 2 through 5 quantify four degrees of increasingly feminized genitalia that lie in the interim. Grade 7 is indistinguishable from grade 6 until puberty, and is thereafter differentiated by the presence of secondary terminal hair; grade 6 is indicated when secondary terminal hair is present, whereas grade 7 is indicated when it is absent. The Quigley scale can be used in conjunction with the traditional three classes of AIS to provide additional information regarding the degree of genital masculinization, and is particularly useful when the diagnosis is PAIS.

Partial androgen insensitivity syndrome is diagnosed when the degree of androgen insensitivity in an individual with a 46,XY karyotype is great enough to partially prevent the masculinization of the genitalia, but is not great enough to completely prevent genital masculinization. This includes any phenotype resulting from androgen insensitivity where the genitalia is partially, but not completely masculinized. Genital ambiguities are frequently detected during clinical examination at birth, and consequently, a PAIS diagnosis can be made during infancy as part of a differential diagnostic workup.

Pubertal undervirilization is common, including gynecomastia, decreased secondary terminal hair, and / or a high pitched voice. The phallic structure ranges from a penis with varying degrees of diminished size and hypospadias to a slightly enlarged clitoris. Wolffian structures (the epididymides, vasa deferentia, and seminal vesicles) are typically partially or fully developed. The prostate is typically small or impalpable. Müllerian remnants are rare, but have been reported.

The gonads in individuals with PAIS are testes, regardless of phenotype; during the embryonic stage of development, testes form in an androgen-independent process that occurs due to the influence of the SRY gene on the Y chromosome. Cryptorchidism is common, and carries with it a 50% risk of germ cell malignancy. If the testes are located intrascrotally, there may still be significant risk of germ cell malignancy; studies have not yet been published to assess this risk.

Predominantly male phenotypes vary in the degree of genital undermasculinization to include micropenis, chordee, scrotum, and / or pseudovaginal perineoscrotal hypospadias. Impotence may be fairly common, depending on phenotypic features; in one study of 15 males with PAIS, 80% of those interviewed indicated that they had some degree of impotence. Anejaculation appears to occur somewhat independently of impotence; some men are still able to ejaculate despite impotence, and others without erectile difficulties cannot. Predominantly female phenotypes include a variable degree of labial fusion and clitoromegaly. Ambiguous phenotypic states include a phallic structure that is intermediate between a clitoris and a penis, and a single perineal orifice that connects to both the urethra and the vagina (i.e. urogenital sinus). At birth, it may not be possible to immediately differentiate the external genitalia of individuals with PAIS as being either male or female, although the majority of individuals with PAIS are raised male.

Given the wide diversity of phenotypes associated with PAIS, the diagnosis is often further specified by assessing genital masculinization. Grades 2 through 5 of the Quigley scale quantify four degrees of increasingly feminized genitalia that correspond to PAIS.

Grade 2, the mildest form of PAIS, presents with a predominantly male phenotype that presents with minor signs of undermasculinized genitalia, such as isolated hypospadias, which can be severe. Hypospadias may manifest with a partially formed channel from the urethral opening to the glans. Until recently, it was thought that isolated micropenis was not a manifestation of PAIS. However, in 2010, two cases of PAIS manifesting with isolated micropenis were documented.

Grade 3, the most common phenotypic form of PAIS, features a predominantly male phenotype that is more severely undermasculinized, and typically presents with micropenis and pseudovaginal perineoscrotal hypospadias with scrotum.

Grade 4 presents with a gender ambiguous phenotype, including a phallic structure that is intermediate between a clitoris and a penis. The urethra typically opens into a common channel with the vagina (i.e. urogenital sinus).

Grade 5, the form of PAIS with the greatest degree of androgen insensitivity, presents with a mostly female phenotype, including separate urethral and vaginal orifices, but also shows signs of slight masculinization including mild clitoromegaly and / or partial labial fusion.

Previously, it was erroneously thought that individuals with PAIS were always infertile; at least one case report has been published that describes fertile men that fit the criteria for grade 2 PAIS (micropenis, penile hypospadias, and gynecomastia).

XX male syndrome is a rare congenital condition where an individual with a female genotype has phenotypically male characteristics that can vary between cases. In 90% of these individuals the syndrome is caused by unequal crossing over between X and Y chromosomes during meiosis in the father, and results in the X chromosome containing the SRY gene, as opposed to the Y chromosome where it is normally found. When the X with the SRY gene combines with a normal X from the mother during fertilization, the result is an XX male. Less common are SRY-negative XX males which can be caused by a mutation in an autosomal or X chromosomal gene. The masculinization of XX males is variable.

This syndrome is diagnosed through various detection methods and occurs in approximately 1:20 000 newborn males, making it less common than Klinefelter syndrome. Treatment is medically unnecessary, although some individuals choose to undergo treatments to make them appear more male or female. It is also called de la Chapelle syndrome, for Albert de la Chapelle, who characterized it in 1972.

Individuals with complete androgen insensitivity syndrome (grades 6 and 7 on the Quigley scale) are born phenotypically female, without any signs of genital masculinization, despite having a 46,XY karyotype. Symptoms of CAIS do not appear until puberty, which may be slightly delayed, but is otherwise normal except for absent menses and diminished or absent secondary terminal hair. Axillary hair (i.e. armpit hair) fails to develop in one third of all cases. External genitalia is normal, although the labia and clitoris are sometimes underdeveloped. The vaginal depth varies widely, but is typically shorter than unaffected women; one study of eight women with CAIS measured the average vaginal depth to be 5.9 cm (vs. 11.1 ± 1.0 cm for unaffected women ). In some extreme cases, the vagina has been reported to be aplastic (resembling a "dimple"), though the exact incidence of this is unknown.

The gonads in these women are not ovaries, but instead, are testes; during the embryonic stage of development, testes form in an androgen-independent process that occurs due to the influence of the SRY gene on the Y chromosome. They may be located intra-abdominally, at the internal inguinal ring, or may herniate into the labia majora, often leading to the discovery of the condition. Testes in affected women have been found to be atrophic upon gonadectomy. Testosterone produced by the testes cannot be directly used due to the mutant androgen receptor that characterizes CAIS; instead, it is aromatized into estrogen, which effectively feminizes the body and accounts for the normal female phenotype observed in CAIS.

Immature sperm cells in the testes do not mature past an early stage, as sensitivity to androgens is required in order for spermatogenesis to complete. Germ cell malignancy risk, once thought to be relatively high, is now thought to be approximately 2%. Wolffian structures (the epididymides, vasa deferentia, and seminal vesicles) are typically absent, but will develop at least partially in approximately 30% of cases, depending on which mutation is causing the CAIS. The prostate, like the external male genitalia, cannot masculinize in the absence of androgen receptor function, and thus remains in the female form.

The Müllerian system (the fallopian tubes, uterus, and upper portion of the vagina) typically regresses due to the presence of anti-Müllerian hormone originating from the Sertoli cells of the testes. These women are thus born without fallopian tubes, a cervix, or a uterus, and the vagina ends "blindly" in a pouch. Müllerian regression does not fully complete in approximately one third of all cases, resulting in Müllerian "remnants". Although rare, a few cases of women with CAIS and fully developed Müllerian structures have been reported. In one exceptional case, a 22-year-old with CAIS was found to have a normal cervix, uterus, and fallopian tubes. In an unrelated case, a fully developed uterus was found in a 22-year-old adult with CAIS.

Other subtle differences that have been reported include slightly longer limbs and larger hands and feet due to a proportionally greater stature than unaffected women, larger teeth, minimal or no acne, well developed breasts, and a greater incidence of meibomian gland dysfunction (i.e. dry eye syndromes and light sensitivity).

Swyer syndrome represents one phenotypic result of a failure of the gonads to develop properly, and hence is part of a class of conditions termed gonadal dysgenesis. There are many forms of gonadal dysgenesis.

Swyer syndrome is an example of a condition in which an externally unambiguous female body carries dysgenetic, atypical, or abnormal gonads. Other examples include complete androgen insensitivity syndrome, partial X chromosome deletions, lipoid congenital adrenal hyperplasia, and Turner syndrome.

At puberty, most affected individuals require treatment with the male sex hormone testosterone to induce development of male secondary sex characteristics such as facial hair and deepening of the voice (masculinization). Hormone treatment can also help prevent breast enlargement (gynecomastia). Adults with this disorder are usually shorter than average for males and are unable to have children (infertile).

In this situation the testes are abnormal, atrophic, or absent, and sperm production severely disturbed to absent. FSH levels tend to be elevated (hypergonadotropic) as the feedback loop is interrupted (lack of feedback inhibition on FSH). The condition is seen in 49–93% of men with azoospermia. Testicular failure includes absence of failure production as well as low production and maturation arrest during the process of spermatogenesis.

Causes for testicular failure include congenital issues such as in certain genetic conditions (e.g. Klinefelter syndrome), some cases of cryptorchidism or Sertoli cell-only syndrome as well as acquired conditions by infection (orchitis), surgery (trauma, cancer), radiation, or other causes. Mast cells releasing inflammatory mediators appear to directly suppress sperm motility in a potentially reversible manner, and may be a common pathophysiological mechanism for many causes leading to inflammation. Testicular azoospermia is a kind of non-obstructive azoospermia.

Generally, men with unexplained hypergonadotropic azoospermia need to undergo a chromosomal evaluation.

Swyer syndrome, or XY gonadal dysgenesis, is a type of hypogonadism in a person whose karyotype is 46,XY. The person is externally female with streak gonads, and if left untreated, will not experience puberty. Such gonads are typically surgically removed (as they have a significant risk of developing tumors) and a typical medical treatment would include hormone replacement therapy.

The syndrome was named by Gerald Swyer, an endocrinologist, based in London, United Kingdom.

Pretesticular azoospermia is characterized by inadequate stimulation of otherwise normal testicles and genital tract. Typically, follicle-stimulating hormone (FSH) levels are low (hypogonadotropic) commensurate with inadequate stimulation of the testes to produce sperm. Examples include hypopituitarism (for various causes), hyperprolactinemia, and exogenous FSH suppression by testosterone. Chemotherapy may suppress spermatogenesis. Pretesticular azoospermia is seen in about 2% of azoospermia. Pretesticular azoospermia is a kind of non-obstructive azoospermia.

All forms of androgen insensitivity are associated with infertility, though exceptions have been reported for both the mild and partial forms.

PAIS is associated with a 50% risk of germ cell malignancy when the testes are undescended. If the testes are located intrascrotally, there may still be significant risk of germ cell malignancy; studies have not yet been published to assess this risk. Some men with PAIS may experience sexual dysfunction including impotence and anejaculation. A few AR mutations that cause PAIS are also associated with prostate and breast cancers.

Vaginal hypoplasia, a relatively frequent finding in CAIS and some forms of PAIS, is associated with sexual difficulties including vaginal penetration difficulties and dyspareunia.

At least one study indicates that individuals with an intersex condition may be more prone to psychological difficulties, due at least in part to parental attitudes and behaviors, and concludes that preventative long-term psychological counseling for parents as well as for affected individuals should be initiated at the time of diagnosis.

Lifespan is not thought to be affected by AIS.

Individuals with mild (or minimal) androgen insensitivity syndrome (grade 1 on the Quigley scale) are born phenotypically male, with fully masculinized genitalia; this category of androgen insensitivity is diagnosed when the degree of androgen insensitivity in an individual with a 46,XY karyotype is great enough to impair virilization or spermatogenesis, but is not great enough to impair normal male genital development. MAIS is the mildest and least known form of androgen insensitivity syndrome.

The existence of a variant of androgen insensitivity that solely affected spermatogenesis was theoretical at first. Cases of phenotypically normal males with isolated spermatogenic defect due to AR mutation were first detected as the result of male infertility evaluations. Until then, early evidence in support of the existence of MAIS was limited to cases involving a mild defect in virilization, although some of these early cases made allowances for some degree of impairment of genital masculinization, such as hypospadias or micropenis. It is estimated that 2-3% of infertile men have AR gene mutations.

Examples of MAIS phenotypes include isolated infertility (oligospermia or azoospermia), mild gynecomastia in young adulthood, decreased secondary terminal hair, high pitched voice, or minor hypospadias repair in childhood. The external male genitalia (penis, scrotum, and urethra) are otherwise normal in individuals with MAIS. Internal genitalia, including Wolffian structures (the epididymides, vasa deferentia, and seminal vesicles) and the prostate, is also normal, although the bitesticular volume of infertile men (both with and without MAIS) is diminished; male infertility is associated with reduced bitesticular volume, varicocele, retractile testes, low ejaculate volume, male accessory gland infections (MAGI), and mumps orchitis. The incidence of these features in infertile men with MAIS is similar to that of infertile men without MAIS. MAIS is not associated with Müllerian remnants.

Individuals with 5-ARD are born with male gonads, including testicles and Wolffian structures. They can have normal male external genitalia, ambiguous genitalia, or normal female genitalia, but usually tend towards a female appearance. As a consequence, they are often raised as girls, but usually have a male gender identity.

The development of the genital tubercle tissue (which by week 9 of a fetus' gestation becomes either a clitoris or a penis) tends towards a size qualifying it as an ambiguous macroclitoris/micropenis (large clitoris/small penis), and the urethra may attach to the phallus.

If the condition has not already been diagnosed, it usually becomes apparent at puberty around age twelve with primary amenorrhoea and virilization. This may include descending of the testes, hirsutism (facial/body hair considered normal in males - not to be confused with hypertrichosis), deepening of the voice, and enlargement of the clitoris into what would then be classed as a penis.

In adulthood, individuals do not experience male-pattern baldness. As DHT is a far more potent androgen than testosterone alone, virilization in those lacking DHT may be absent or reduced compared to males with functional 5-AR. It is hypothesized that rising testosterone levels at the start of puberty are able to generate sufficient levels of DHT either by the action of 5α-reductase type I (active in the adult liver, non-genital skin and some brain areas) or through the expression of low levels of 5α-reductase type II in the testes.

5-ARD is associated with an increased risk of cryptorchidism and testicular cancer.

All forms of androgen insensitivity, including CAIS, are associated with infertility, though exceptions have been reported for both the mild and partial forms.

CAIS is associated with a decreased bone mineral density. Some have hypothesized that the decreased bone mineral density observed in women with CAIS is related to the timing of gonadectomy and inadequate estrogen supplementation. However, recent studies show that bone mineral density is similar whether gonadectomy occurs before or after puberty, and is decreased despite estrogen supplementation, leading some to hypothesize that the deficiency is directly attributable to the role of androgens in bone mineralization.

CAIS is also associated with an increased risk for gonadal tumors (e.g. germ cell malignancy) in adulthood if gonadectomy is not performed. The risk of malignant germ cell tumors in women with CAIS increases with age and has been estimated to be 3.6% at 25 years and 33% at 50 years. The incidence of gonadal tumors in childhood is thought to be relatively low; a recent review of the medical literature found that only three cases of malignant germ cell tumors in prepubescent girls have been reported in association with CAIS in the last 100 years. Some have estimated the incidence of germ cell malignancy to be as low as 0.8% before puberty.

Vaginal hypoplasia, a relatively frequent finding in CAIS and some forms of PAIS, is associated with sexual difficulties including vaginal penetration difficulties and dyspareunia.

At least one study indicates that individuals with an intersex condition may be more prone to psychological difficulties, due at least in part to parental attitudes and behaviors, and concludes that preventative long-term psychological counseling for parents as well as for affected individuals should be initiated at the time of diagnosis.

Lifespan is not thought to be affected by AIS.

Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy's disease, is a severe neurodegenerative syndrome that is associated with a particular mutation of the androgen receptor's polyglutamine tract called a trinucleotide repeat expansion. SBMA results when the length of the polyglutamine tract exceeds 40 repetitions.

Although technically a variant of MAIS, SBMA's presentation is not typical of androgen insensitivity; symptoms do not occur until adulthood and include neuromuscular defects as well as signs of androgen inaction. Neuromuscular symptoms include progressive proximal muscle weakness, atrophy, and fasciculations. Symptoms of androgen insensitivity experienced by men with SBMA are also progressive and include testicular atrophy, severe oligospermia or azoospermia, gynecomastia, and feminized skin changes despite elevated androgen levels. Disease onset, which usually affects the proximal musculature first, occurs in the third to fifth decades of life, and is often preceded by muscular cramps on exertion, tremor of the hands, and elevated muscle creatine kinase. SBMA is often misdiagnosed as amyotrophic lateral sclerosis (ALS) (also known as Lou Gehrig's disease).

The symptoms of SBMA are thought to be brought about by two simultaneous pathways involving the toxic misfolding of proteins and loss of AR functionality. The polyglutamine tract in affected pedigrees tends to increase in length over generations, a phenomenon known as "anticipation", leading to an increase in the severity of the disease as well as a decrease in the age of onset for each subsequent generation of a family affected by SBMA.

AIS is broken down into three classes based on phenotype: complete androgen insensitivity syndrome (CAIS), partial androgen insensitivity syndrome (PAIS), and mild androgen insensitivity syndrome (MAIS). A supplemental system of phenotypic grading that uses seven classes instead of the traditional three was proposed by pediatric endocrinologist Charmian A. Quigley et al. in 1995. The first six grades of the scale, grades 1 through 6, are differentiated by the degree of genital masculinization; grade 1 is indicated when the external genitalia is fully masculinized, grade 6 is indicated when the external genitalia is fully feminized, and grades 2 through 5 quantify four degrees of decreasingly masculinized genitalia that lie in the interim. Grade 7 is indistinguishable from grade 6 until puberty, and is thereafter differentiated by the presence of secondary terminal hair; grade 6 is indicated when secondary terminal hair is present, whereas grade 7 is indicated when it is absent. The Quigley scale can be used in conjunction with the traditional three classes of AIS to provide additional information regarding the degree of genital masculinization, and is particularly useful when the diagnosis is PAIS.

As babies and children, XXY males may have weaker muscles and reduced strength. As they grow older, they tend to become taller than average. They may have less muscle control and coordination than other boys of their age.

During puberty, the physical traits of the syndrome become more evident; because these boys do not produce as much testosterone as other boys, they have a less muscular body, less facial and body hair, and broader hips. As teens, XXY males may develop breast tissue and also have weaker bones, and a lower energy level than other males.

By adulthood, XXY males look similar to males without the condition, although they are often taller. In adults, possible characteristics vary widely and include little to no sign of affectedness, a , youthful build and facial appearance, or a rounded body type with some degree of gynecomastia (increased breast tissue). Gynecomastia is present to some extent in about a third of affected individuals, a slightly higher percentage than in the XY population. About 10% of XXY males have gynecomastia noticeable enough that they may choose to have cosmetic surgery.

Affected males are often infertile, or may have reduced fertility. Advanced reproductive assistance is sometimes possible.

The term "hypogonadism" in XXY symptoms is often misinterpreted to mean "small testicles" when it means decreased testicular hormone/endocrine function. Because of this (primary) hypogonadism, individuals will often have a low serum testosterone level but high serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels. Despite this misunderstanding of the term, however, it is true that XXY men may also have microorchidism (i.e., small testicles).

The testicle size of affected males are usually less than 2 cm in length (and always shorter than 3.5 cm), 1 cm in width and 4 ml in volume.

XXY males are also more likely than other men to have certain health problems that typically affect females, such as autoimmune disorders, breast cancer, venous thromboembolic disease, and osteoporosis. In contrast to these potentially increased risks, it is currently thought that rare X-linked recessive conditions occur less frequently in XXY males than in normal XY males, since these conditions are transmitted by genes on the X chromosome, and people with two X chromosomes are typically only carriers rather than affected by these X-linked recessive conditions.

Pseudohermaphroditism, or pseudo-hermaphroditism, is an old clinical term for an organism is born with primary sex characteristics of one sex but develops the secondary sex characteristics that are different from what would be expected on the basis of the gonadal tissue (ovary or testis). It can be contrasted with the term true hermaphroditism, which described a condition where testicular and ovarian tissue were present in the same individual. This language has fallen out of favor due to misconceptions and pejorative connotations associated with the terms, and also a shift to nomenclature based on genetics.

The term "male pseudohermaphrodite" was used when a testis is present, and the term "female pseudohermaphrodite" was used when an ovary is present.

In some cases, external sex organs associated with pseudohermaphroditism look intermediate between a typical clitoris and penis. In other cases, the external sex organs have an appearance that would be expected to be seen with the "opposite" gonadal tissue. Because of this, pseudohermaphroditism is sometimes not identified until puberty or adulthood.

Associated conditions include 5-α-reductase deficiency and androgen insensitivity syndrome.

Androgen insensitivity syndrome (AIS) is an intersex condition in which there is a partial or complete inability of many cells in the affected genetic male to respond to androgenic hormones. This can prevent or impair the masculinization of male genitalia in the developing genetic male (chromosomal XY) fetus, as well as the development of male secondary sexual characteristics at puberty. Clinical phenotypes range from a normal male habitus with mild spermatogenic defect or reduced secondary terminal hair; to a full female habitus despite the presence of a Y-chromosome. Women (chromosomal XX) who are heterozygous for the AR gene have normal primary and secondary sexual characteristics; this female carrier will pass the affected AR gene to any child she has with 50% likelihood. AIS is the largest single entity that leads to 46,XY undermasculinized genitalia.

The androgen receptor (AR), which is defective due to a mutation in most of these syndromes, is a type of nuclear receptor that is activated by binding to either of the androgenic hormones (testosterone or dihydrotestosterone) in the cytoplasm, and then translocates into the nucleus where it binds to DNA, provided androgen response elements and coactivators are present. This combination functions as a transcription complex to turn on androgen gene expression. Thus the AR activates these genes to mediate the effects of androgens in the human body, including the development and maintenance of the male sexual phenotype and generalized anabolic effects. Over 400 AR mutations have been reported.

AIS is divided into three categories that are differentiated by the degree of genital masculinization: complete androgen insensitivity syndrome (CAIS) is indicated when the external genitalia are that of a normal female; mild androgen insensitivity syndrome (MAIS) is indicated when the external genitalia are that of a normal male, and partial androgen insensitivity syndrome (PAIS) is indicated when the external genitalia are partially, but not fully, masculinized.

Management of AIS is currently limited to symptomatic management; no method is currently available to correct the malfunctioning androgen receptor proteins produced by "AR" gene mutations. Areas of management include sex assignment, genitoplasty, gonadectomy in relation to tumor risk, hormone replacement therapy, genetic counseling, and psychological counseling.

The condition may be due to:

- Turner syndrome, and its variations (i.e. mosaicism)

- XX gonadal dysgenesis, also pure gonadal dysgenesis, 46,XX

- Swyer syndrome, also pure gonadal dysgenesis, 46,XY

- Perrault syndrome, XX gonadal dysgenesis + sensorineural hearing loss

- Mixed gonadal dysgenesis

- Exposure to environmental endocrine disruptors

Gonadal dysgenesis is any congenital developmental disorder of the reproductive system characterized by a progressive loss of germ cells on the developing gonads of an embryo. This loss leads to extremely hypoplastic (underdeveloped) and dysfunctioning gonads mainly composed of fibrous tissue, hence the name streak gonads—i.e., a form of aplasia in which the ovary is replaced by functionless tissue. The accompanying hormonal failure also prevents the development of secondary sex characteristics in either sex, resulting in a sexually infantile female appearance and infertility.

The first type of gonadal dysgenesis discovered was Turner syndrome.

Anorchia (or anorchism) is an XY disorder of sex development in which individuals have both testes absent at birth. Within a few weeks of fertilization, the embryo develops rudimentary gonads (testes), which produce hormones responsible for the development of the reproductive system. If the testes fail to develop within eight weeks, the baby will develop female genitalia (see Swyer syndrome). If the testes begin to develop but are lost or cease to function between eight and 10 weeks, the baby will have ambiguous genitalia when it is born. However, if the testes are lost after 14 weeks, the baby will have partial male genitalia with the notable absence of gonads.

Tests include observable lack of testes, low testosterone levels (typical female levels), elevated follicle stimulating hormone and luteinizing hormone levels, XY karyotype, ultrasound or magnetic resonance imaging showing absent gonadal tissue, low bone density, low anti-Müllerian hormone levels, and surgical exploration for evidence of male gonadal tissue.

Some degree of language learning or reading impairment may be present, and neuropsychological testing often reveals deficits in executive functions, although these deficits can often be overcome through early intervention. There may also be delays in motor development which can be addressed through occupational therapy and physical therapy. XXY males may sit up, crawl, and walk later than other infants; they may also struggle in school, both academically and with sports.

5α-Reductase deficiency (5-ARD) is an autosomal recessive intersex condition caused by a mutation of the 5α reductase type II gene.

Sertoli cell only syndrome is likely multifactorial, and characterized by severely reduced or absent spermatogenesis despite the presence of both Sertoli and Leydig cells. A substantial subset of men with this uncommon syndrome have microdeletions in the Yq11 region of the Y chromosome, an area known as the AZF (azoospermia factor) region. Generally speaking, testosterone and LH levels are normal, but due to lack of inhibin, FSH levels are increased.