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Androgen insensitivity syndrome (AIS) is a difference in sex development involving hormonal resistance due to androgen receptor dysfunction. It affects 1 in 20,000 to 64,000 XY ( karyotypically male) births. The condition results in the partial or complete inability of
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
to respond to androgens. This unresponsiveness can impair or prevent the development of male genitals, as well as impairing or preventing the development of male
secondary sexual characteristics Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a ...
at
puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a ...
. It does not significantly impair female genital or sexual development. The insensitivity to androgens is therefore clinically significant only when it occurs in genetic males, (i.e. individuals with a
Y-chromosome The Y chromosome is one of two sex chromosomes ( allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or ...
, or more specifically, an SRY gene). Clinical
phenotypes In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological prop ...
in these individuals range from a typical male habitus with mild spermatogenic defect or reduced secondary terminal hair, to a full female habitus, despite the presence of a Y-chromosome. 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 those of a typical female; mild androgen insensitivity syndrome (MAIS) is indicated when the external genitalia are those of a typical male, and partial androgen insensitivity syndrome (PAIS) is indicated when the external genitalia are partially, but not fully, masculinized. Androgen insensitivity syndrome is the largest single entity that leads to 46,XY undermasculinized genitalia. 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 to reduce
tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
risk, hormone replacement therapy,
genetic counseling Genetic counseling is the process of investigating individuals and families affected by or at risk of genetic disorders to help them understand and adapt to the medical, psychological and familial implications of genetic contributions to disease; t ...
, and
psychological counseling Psychotherapy (also psychological therapy, talk therapy, or talking therapy) is the use of psychological methods, particularly when based on regular personal interaction, to help a person change behavior, increase happiness, and overcome prob ...
.


Genetics

The human androgen receptor (AR) is a protein encoded by a
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
located on the
proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position ...
long arm of the
X chromosome The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...
( locus Xq11-Xq12). The
protein coding region The coding region of a gene, also known as the coding sequence (CDS), is the portion of a gene's DNA or RNA that codes for protein. Studying the length, composition, regulation, splicing, structures, and functions of coding regions compared to n ...
consists of approximately 2,757 nucleotides (919 codons) spanning eight
exons An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding seque ...
, designated 1-8 or A-H. Introns vary in size between 0.7 and 26 kb. Like other nuclear receptors, the AR protein consists of several functional domains: the transactivation domain (also called the transcription-regulation domain or the amino / NH2-terminal domain), the DNA-binding domain, the hinge region, and the steroid-binding domain (also called the
carboxyl-terminal The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain ( protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...
ligand-binding domain). The transactivation domain is encoded by exon 1, and makes up more than half of the AR protein. Exons 2 and 3 encode the DNA-binding domain, while the 5' portion of exon 4 encodes the hinge region. The remainder of exons 4 through 8 encodes the ligand binding domain.


Trinucleotide satellite lengths and AR transcriptional activity

The AR gene contains two polymorphic trinucleotide microsatellites in exon 1. The first microsatellite (nearest the 5' end) contains 8 to 60 repetitions of the glutamine
codon The genetic code is the set of rules used by living cells to translate information encoded within genetic material ( DNA or RNA sequences of nucleotide triplets, or codons) into proteins. Translation is accomplished by the ribosome, which links ...
"CAG" and is thus known as the polyglutamine tract. The second microsatellite contains 4 to 31 repetitions of the glycine codon "GGC" and is known as the polyglycine tract. The average number of repetitions varies by ethnicity, with Caucasians exhibiting an average of 21 CAG repeats, and Blacks 18. In men, disease states are associated with extremes in polyglutamine tract length; prostate cancer,
hepatocellular carcinoma Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is currently the most common cause of death in people with cirrhosis. HCC is the third leading cause of cancer-related deaths worldwide. It occurs in t ...
, and intellectual disability are associated with too few repetitions, while spinal and bulbar muscular atrophy (SBMA) is associated with a CAG repetition length of 40 or more. Some studies indicate that the length of the polyglutamine tract is inversely correlated with transcriptional activity in the AR protein, and that longer polyglutamine tracts may be associated with
male infertility Male infertility refers to a sexually mature male's inability to impregnate a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen ...
and undermasculinized genitalia in men. However, other studies have indicated no such correlation exists. A comprehensive
meta-analysis A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting m ...
of the subject published in 2007 supports the existence of the correlation, and concluded these discrepancies could be resolved when
sample size Sample size determination is the act of choosing the number of observations or replicates to include in a statistical sample. The sample size is an important feature of any empirical study in which the goal is to make inferences about a populati ...
and study design are taken into account. Some studies suggest longer polyglycine tract lengths are also associated with genital masculinization defects in men. Other studies find no such association.


AR mutations

As of 2010, over 400 ''AR'' mutations have been reported in the ''AR'' mutation database, and the number continues to grow.
Inheritance Inheritance is the practice of receiving private property, titles, debts, entitlements, privileges, rights, and obligations upon the death of an individual. The rules of inheritance differ among societies and have changed over time. Of ...
is typically maternal and follows an X-linked recessive pattern; individuals with a 46,XY karyotype always express the mutant gene since they have only one
X chromosome The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...
, whereas 46,XX carriers are minimally affected. About 30% of the time, the ''AR'' mutation is a spontaneous result, and is not inherited. Such ''de novo'' mutations are the result of a
germ cell Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embr ...
mutation or germ cell mosaicism in the gonads of one of the parents, or a mutation in the fertilized egg itself. In one study, three of eight ''de novo'' mutations occurred in the postzygotic stage, leading to the estimate that up to one-third of ''de novo'' mutations result in somatic mosaicism. Not every mutation of the ''AR'' gene results in androgen insensitivity; one particular mutation occurs in 8 to 14% of genetic males, and is thought to adversely affect only a small number of individuals when other genetic factors are present.


Other causes

Some individuals with CAIS or PAIS do not have any ''AR'' mutations despite clinical, hormonal, and histological features sufficient to warrant an AIS diagnosis; up to 5% of women with CAIS do not have an ''AR'' mutation, as well as between 27 and 72% of individuals with PAIS. In one patient, the underlying cause for presumptive PAIS was a mutant steroidogenic factor-1 (SF-1) protein. In another patient, CAIS was the result of a deficit in the transmission of a transactivating signal from the
N-terminal The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...
region of the androgen receptor to the basal transcription machinery of the cell. A coactivator protein interacting with the activation function 1 (AF-1) transactivation domain of the androgen receptor may have been deficient in this patient. The signal disruption could not be corrected by supplementation with any coactivators known at the time, nor was the absent coactivator protein characterized, which left some in the field unconvinced that a mutant coactivator would explain the mechanism of androgen resistance in CAIS or PAIS patients with a typical ''AR'' gene.


XY karyotype

Depending on the mutation, a person with a 46,XY karyotype and AIS can have either a male (MAIS) or female (CAIS) phenotype, or may have genitalia that are only partially masculinized (PAIS). The gonads are testes regardless of phenotype due to the influence of the Y chromosome. A 46,XY female, thus, does not have ovaries, and can not contribute an egg towards conception. In some cases, 46, XY females do form a vestigial
uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
and have been able to
gestate Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during preg ...
children. Such examples are rare and have required the use of an egg donor, hormone therapy, and IVF. Several case studies of fertile 46,XY males with AIS have been published, although this group is thought to be a minority. In some cases, infertile males with MAIS have been able to conceive children after increasing their sperm count through the use of supplementary testosterone. A genetic male conceived by a man with AIS would not receive his father's
X chromosome The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...
, thus would neither inherit nor carry the gene for the syndrome. A genetic female conceived in such a way would receive her father's X chromosome, thus would become a
carrier Carrier may refer to: Entertainment * ''Carrier'' (album), a 2013 album by The Dodos * ''Carrier'' (board game), a South Pacific World War II board game * ''Carrier'' (TV series), a ten-part documentary miniseries that aired on PBS in April 20 ...
.


XX karyotype

Genetic females (46,XX karyotype) have two X chromosomes, thus have two ''AR'' genes. A mutation in one (but not both) results in a minimally affected, fertile, female carrier. Some carriers have been noted to have slightly reduced body hair, delayed puberty, and/or tall stature, presumably due to skewed X-inactivation. A female carrier will pass the affected ''AR'' gene to her children 50% of the time. If the affected child is a genetic female, she, too, will be a carrier. An affected 46,XY child will have AIS. A genetic female with mutations in both ''AR'' genes could theoretically result from the union of a fertile man with AIS and a female carrier of the gene, or from ''de novo'' mutation. However, given the scarcity of fertile AIS men and low incidence of ''AR'' mutation, the chances of this occurrence are small. The
phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...
of such an individual is a matter of speculation; as of 2010, no such documented case has been published.


Correlation of genotype and phenotype

Individuals with partial AIS, unlike those with the complete or mild forms, present at birth with
ambiguous genitalia Intersex people are individuals born with any of several sex characteristics including chromosome patterns, gonads, or genitals that, according to the Office of the United Nations High Commissioner for Human Rights, "do not fit typical ...
, and the decision to raise the child as male or female is often not obvious. Unfortunately, little information regarding
phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...
can be gleaned from precise knowledge of the ''AR'' mutation itself; the same ''AR ''mutation may cause significant variation in the degree of masculinization in different individuals, even among members of the same family. Exactly what causes this variation is not entirely understood, although factors contributing to it could include the lengths of the polyglutamine and polyglycine tracts, sensitivity to and variations in the intrauterine endocrine milieu, the effect of coregulatory proteins active in Sertoli cells, somatic mosaicism, expression of the ''5RD2''
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
in genital skin fibroblasts, reduced ''AR'' transcription and
translation Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...
from factors other than mutations in the AR coding region, an unidentified coactivator protein, enzyme deficiencies such as 21-hydroxylase deficiency, or other genetic variations such as a mutant steroidogenic factor-1 protein. The degree of variation, however, does not appear to be constant across all ''AR'' mutations, and is much more extreme in some. Missense mutations that result in a single amino acid substitution are known to produce the most phenotypic diversity.


Pathophysiology


Androgens and the androgen receptor

The effects that androgens have on the human body ( virilization, masculinization, anabolism, etc.) are not brought about by androgens themselves, but rather are the result of androgens bound to androgen receptors; the androgen receptor mediates the effects of androgens in the human body. Likewise, the androgen receptor itself is generally inactive in the cell until androgen binding occurs. The following series of steps illustrates how androgens and the androgen receptor work together to produce androgenic effects: In this way, androgens bound to androgen receptors regulate the expression of target genes, thus produce androgenic effects. Theoretically, certain mutant androgen receptors can function without androgens; ''in vitro'' studies have demonstrated that a mutant androgen receptor protein can induce transcription in the absence of androgen if its steroid binding domain is deleted. Conversely, the steroid-binding domain may act to repress the AR transactivation domain, perhaps due to the AR's unliganded conformation.


Androgens in fetal development

Human embryos An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm c ...
develop similarly for the first six weeks, regardless of genetic sex (46,XX or 46,XY karyotype); the only way to tell the difference between 46,XX or 46,XY embryos during this time period is to look for
Barr bodies A Barr body (named after discoverer Murray Barr) or X-chromatin is an inactive X chromosome in a cell with more than one X chromosome, rendered inactive in a process called lyonization, in species with XY sex-determination (including human ...
or a Y chromosome. The gonads begin as bulges of tissue called the genital ridges at the back of the
abdominal cavity The abdominal cavity is a large body cavity in humans and many other animals that contains many organs. It is a part of the abdominopelvic cavity. It is located below the thoracic cavity, and above the pelvic cavity. Its dome-shaped roof is th ...
, near the midline. By the fifth week, the genital ridges differentiate into an outer cortex and an inner medulla, and are called indifferent gonads. By the sixth week, the indifferent gonads begin to differentiate according to genetic sex. If the karyotype is 46,XY, testes develop due to the influence of the
Y chromosome The Y chromosome is one of two sex chromosomes (allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or abs ...
’s ''SRY'' gene. This process does not require the presence of androgen, nor a functional androgen receptor. Until around the seventh week of development, the embryo has indifferent sex accessory ducts, which consist of two pairs of ducts: the Müllerian ducts and the Wolffian ducts. Sertoli cells within the testes secrete anti-Müllerian hormone around this time to suppress the development of the Müllerian ducts, and cause their degeneration. Without this anti-Müllerian hormone, the Müllerian ducts develop into the female internal genitalia (
uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...
,
cervix The cervix or cervix uteri (Latin, 'neck of the uterus') is the lower part of the uterus (womb) in the human female reproductive system. The cervix is usually 2 to 3 cm long (~1 inch) and roughly cylindrical in shape, which changes during ...
,
fallopian tubes The fallopian tubes, also known as uterine tubes, oviducts or salpinges (singular salpinx), are paired tubes in the human female that stretch from the uterus to the ovaries. The fallopian tubes are part of the female reproductive system. In ot ...
, and upper vaginal barrel). Unlike the Müllerian ducts, the Wolffian ducts will not continue to develop by default. In the presence of testosterone and functional androgen receptors, the Wolffian ducts develop into the
epididymides The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is a single, narrow, tightly-coiled tube in adult humans, in length. It serves as an interconnection between t ...
, vasa deferentia, and seminal vesicles. If the testes fail to secrete testosterone, or the androgen receptors do not function properly, the Wolffian ducts degenerate. Masculinization of the
male external genitalia A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, ...
(the
penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...
, penile
urethra The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra ...
, and
scrotum The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum co ...
), as well as the prostate, are dependent on the androgen
dihydrotestosterone Dihydrotestosterone (DHT, 5α-dihydrotestosterone, 5α-DHT, androstanolone or stanolone) is an endogenous androgen sex steroid and hormone. The enzyme 5α-reductase catalyzes the formation of DHT from testosterone in certain tissues includi ...
. Testosterone is converted into dihydrotestosterone by the 5-alpha reductase enzyme. If this enzyme is absent or deficient, then dihydrotestosterone is not created, and the external male genitalia do not develop properly. As is the case with the internal male genitalia, a functional androgen receptor is needed for dihydrotestosterone to regulate the transcription of target genes involved in development.


Pathogenesis of AIS

Mutations in the androgen receptor gene can cause problems with any of the steps involved in androgenization, from the synthesis of the androgen receptor protein itself, through the transcriptional ability of the dimerized, androgen-AR complex. AIS can result if even one of these steps is significantly disrupted, as each step is required for androgens to activate the AR successfully and regulate gene expression. Exactly which steps a particular mutation will impair can be predicted, to some extent, by identifying the area of the AR in which the mutation resides. This predictive ability is primarily retrospective in origin; the different functional domains of the AR gene have been elucidated by analyzing the effects of specific mutations in different regions of the AR. For example, mutations in the steroid binding domain have been known to affect androgen binding affinity or retention, mutations in the hinge region have been known to affect nuclear translocation, mutations in the DNA-binding domain have been known to affect dimerization and binding to target DNA, and mutations in the transactivation domain have been known to affect target gene transcription regulation. Unfortunately, even when the affected functional domain is known, predicting the phenotypical consequences of a particular mutation (see Correlation of genotype and phenotype) is difficult. Some mutations can adversely impact more than one functional domain. For example, a mutation in one functional domain can have deleterious effects on another by altering the way in which the domains interact. A single mutation can affect all downstream functional domains if a
premature stop codon In genetics, a nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a ''nonsense codon'' in the transcribed mRNA, and in leading to a truncated, incomplete, and usually nonfunctional protein produ ...
or framing error results; such a mutation can result in a completely unusable (or unsynthesizable) androgen receptor protein. The steroid binding domain is particularly vulnerable to the effects of a premature stop codon or framing error, since it occurs at the end of the gene, and its information is thus more likely to be truncated or misinterpreted than other functional domains. Other, more complex relationships have been observed as a consequence of mutated ''AR''; some mutations associated with male phenotypes have been linked to male breast cancer, prostate cancer, or in the case of spinal and bulbar muscular atrophy, disease of the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
. The form of breast cancer seen in some men with PAIS is caused by a mutation in the AR's DNA-binding domain. This mutation is thought to cause a disturbance of the AR's target gene interaction that allows it to act at certain additional targets, possibly in conjunction with the estrogen receptor protein, to cause cancerous growth. The pathogenesis of spinal and bulbar muscular atrophy (SBMA) demonstrates that even the mutant AR protein itself can result in
pathology Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...
. The trinucleotide repeat expansion of the polyglutamine tract of the AR gene that is associated with SBMA results in the synthesis of a
misfolded Protein folding is the physical process by which a protein chain is translated to its native three-dimensional structure, typically a "folded" conformation by which the protein becomes biologically functional. Via an expeditious and reproduc ...
AR protein that the cell fails to proteolyze and disperse properly. These misfolded AR proteins form aggregates in the cell
cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...
and
nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: * Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...
. Over the course of 30 to 50 years, these aggregates accumulate and have a cytotoxic effect, eventually resulting in the neurodegenerative symptoms associated with SBMA.


Diagnosis

The phenotypes that result from the insensitivity to androgens are not unique to AIS, thus the diagnosis of AIS requires thorough exclusion of other causes. Clinical findings indicative of AIS include the presence of a short vagina or undermasculinized genitalia, partial or complete regression of Müllerian structures, bilateral nondysplastic testes, and impaired
spermatogenesis Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubu ...
and/or virilization. Laboratory findings include a 46,XY karyotype and typical or elevated postpubertal testosterone, luteinizing hormone, and estradiol levels. The androgen binding activity of genital skin fibroblasts is typically diminished, although exceptions have been reported. Conversion of testosterone to dihydrotestosterone may be impaired. The diagnosis of AIS is confirmed if androgen receptor
gene sequencing Gene Sequencing may refer to: * DNA sequencing * or a comprehensive variant of it: Whole genome sequencing Whole genome sequencing (WGS), also known as full genome sequencing, complete genome sequencing, or entire genome sequencing, is the pr ...
reveals a mutation, although not all individuals with AIS (particularly PAIS) will have an ''AR'' mutation (see Other Causes). Each of the three types of AIS (complete, partial, and mild) has a different list of differential diagnoses to consider. Depending on the form of AIS suspected, the list of differentials can include:


Classification

AIS is broken down into three classes based on
phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...
: 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.


Complete AIS


Partial AIS


Mild AIS


Management

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 A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
risk, hormone replacement therapy,
genetic counseling Genetic counseling is the process of investigating individuals and families affected by or at risk of genetic disorders to help them understand and adapt to the medical, psychological and familial implications of genetic contributions to disease; t ...
, and
psychological counseling Psychotherapy (also psychological therapy, talk therapy, or talking therapy) is the use of psychological methods, particularly when based on regular personal interaction, to help a person change behavior, increase happiness, and overcome prob ...
.


CAIS


PAIS


MAIS


Epidemiology

AIS represents about 15% to 20% of DSDs and affects 1 in 20,000 to 1 in 64,000 males. Estimates for the incidence of androgen insensitivity syndrome are based on a relatively small
population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction usi ...
size, thus are known to be imprecise. CAIS is estimated to occur in one of every 20,400 46,XY births. A nationwide survey in the Netherlands based on patients with genetic confirmation of the diagnosis estimates that the minimal incidence of CAIS is one in 99,000. The incidence of PAIS is estimated to be one in 130,000. Due to its subtle presentation, MAIS is not typically investigated except in the case of
male infertility Male infertility refers to a sexually mature male's inability to impregnate a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen ...
, thus its true prevalence is unknown.


Controversy


Preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD or PIGD) refers to genetic profiling of embryos prior to implantation (as a form of embryo profiling), and sometimes even of oocytes prior to fertilization. When used to screen for a specific genetic sequence, its main advantage is that it avoids selective pregnancy termination, as the method makes it highly likely that a selected embryo will be free of the condition under consideration. In the UK, AIS appears on a list of serious genetic diseases that may be screened for via PGD. Some ethicists, clinicians, and intersex advocates have argued that screening embryos to specifically exclude intersex traits is based on social and cultural norms as opposed to medical necessity.


History

Recorded descriptions of the effects of AIS date back hundreds of years, although significant understanding of its underlying histopathology did not occur until the 1950s. The taxonomy and
nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. The principles of naming vary from the relatively informal conventions of everyday speech to the internationally ag ...
associated with androgen insensitivity went through a significant evolution that paralleled this understanding.


Timeline of major milestones

* 1950:
Lawson Wilkins Lawson Wilkins (1894-1963) was a pioneering pediatric endocrinologist. He is known along with John Money for pioneering surgeries for visibly intersex newborns. Honors *Borden Award, American Academy of Pediatrics (1953) *Amory Prize, American A ...
administers daily methyltestosterone to a karyotype, 46,XY female patient, who shows no signs of virilization. His experiment is the first documented demonstration of the pathophysiology of AIS. * 1970:
Mary F. Lyon Mary Frances Lyon (15 May 1925 – 25 December 2014) was an English geneticist best known for her discovery of X-chromosome inactivation, an important biological phenomenon. Early life and education Mary Lyon was born on 15 May 1925 in Norwi ...
and Susan Hawkes reported that a gene on the X chromosome caused complete insensitivity to androgens in mice. * 1981:
Barbara Migeon Barbara Ruben Migeon (born July 31, 1931) is a professor at the Johns Hopkins University Institute of Genetic Medicine. She founded the Johns Hopkins program in Human Genetics and Molecular Biology. Migeon is the author of ''Females are Mosaics: ...
''et al.'' narrowed down the locus of the human androgen receptor gene (or a factor controlling the androgen receptor gene) to somewhere between Xq11 and Xq13. * 1988: The human androgen receptor gene is first
cloned Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, ...
and partially analyzed by multiple parties. Terry Brown ''et al.'' reported the first mutations proven to cause AIS. * 1989: Terry Brown ''et al.'' reported the exact locus of the AR gene (Xq11-Xq12), and Dennis Lubahn ''et al.'' published its intron- exon boundaries. * 1994: The androgen receptor gene mutations database was created to provide a comprehensive listing of mutations published in medical journals and conference proceedings.


Early terminology

The first descriptions of the effects of AIS appeared in the medical literature as individual case reports or as part of a comprehensive description of
intersex Intersex people are individuals born with any of several sex characteristics including chromosome patterns, gonads, or genitals that, according to the Office of the United Nations High Commissioner for Human Rights, "do not fit typical b ...
physicalities. In 1839, Scottish obstetrician Sir
James Young Simpson Sir James Young Simpson, 1st Baronet, (7 June 1811 – 6 May 1870) was a Scottish obstetrician and a significant figure in the history of medicine. He was the first physician to demonstrate the anaesthetic properties of chloroform on humans a ...
published one such description in an exhaustive study of intersexuality that has been credited with advancing the medical community's understanding of the subject. Simpson's system of taxonomy, however, was far from the first; taxonomies or descriptions for the classification of intersexuality were developed by Italian physician and physicist Fortuné Affaitati in 1549, French surgeon Ambroise Paré in 1573, French physician and sexology pioneer Nicolas Venette in 1687 (under the pseudonym Vénitien Salocini), and French zoologist Isidore Geoffroy Saint-Hilaire in 1832. All five of these authors used the colloquial term " hermaphrodite" as the foundation of their taxonomies, although Simpson himself questioned the propriety of the word in his publication. Use of the word "hermaphrodite" in the medical literature has persisted to this day, although its propriety is still in question. An alternative system of nomenclature has been recently suggested, but the subject of exactly which word or words should be used in its place still one of much debate.


Pseudohermaphroditism

" Pseudohermaphroditism" has, until very recently, been the term used in the medical literature to describe the condition of an individual whose gonads and karyotype do not match the external genitalia in the gender binary sense. For example, 46,XY individuals who have a female phenotype, but also have testes instead of ovaries—a group that includes all individuals with CAIS, as well as some individuals with PAIS—are classified as having "male pseudohermaphroditism", while individuals with both an ovary and a testis (or at least one ovotestis) are classified as having " true hermaphroditism". Use of the word in the medical literature antedates the discovery of the chromosome, thus its definition has not always taken karyotype into account when determining an individual's sex. Previous definitions of "pseudohermaphroditism" relied on perceived inconsistencies between the internal and external organs; the "true" sex of an individual was determined by the internal organs, and the external organs determined the "perceived" sex of an individual. German-Swiss pathologist
Edwin Klebs Theodor Albrecht Edwin Klebs (6 February 1834 – 23 October 1913) was a German-Swiss microbiologist. He is mainly known for his work on infectious diseases. His works paved the way for the beginning of modern bacteriology, and inspired Louis ...
is sometimes noted for using the word "pseudohermaphroditism" in his taxonomy of
intersex Intersex people are individuals born with any of several sex characteristics including chromosome patterns, gonads, or genitals that, according to the Office of the United Nations High Commissioner for Human Rights, "do not fit typical b ...
uality in 1876, although the word is clearly not his invention as is sometimes reported; the history of the word " pseudohermaphrodite" and the corresponding desire to separate "true" hermaphrodites from "false", "spurious", or "pseudo" hermaphrodites, dates back to at least 1709, when Dutch anatomist Frederik Ruysch used it in a publication describing a subject with testes and a mostly female phenotype. "Pseudohermaphrodite" also appeared in the '' Acta Eruditorum'' later that same year, in a review of Ruysch's work. Also some evidence indicates the word was already being used by the German and French medical community long before Klebs used it; German physiologist
Johannes Peter Müller Johannes Peter Müller (14 July 1801 – 28 April 1858) was a German physiologist, comparative anatomist, ichthyologist, and herpetologist, known not only for his discoveries but also for his ability to synthesize knowledge. The paramesonephri ...
equated "pseudohermaphroditism" with a subclass of hermaphroditism from Saint-Hilaire's taxonomy in a publication dated 1834, and by the 1840s "pseudohermaphroditism" was appearing in several French and German publications, including dictionaries.


Testicular feminization

In 1953, American
gynecologist Gynaecology or gynecology (see spelling differences) is the area of medicine that involves the treatment of women's diseases, especially those of the reproductive organs. It is often paired with the field of obstetrics, forming the combined ...
John Morris provided the first full description of what he called "testicular feminization syndrome" based on 82 cases compiled from the medical literature, including two of his own patients. The term "testicular feminization" was coined to reflect Morris' observation that the testicles in these patients produced a hormone that had a feminizing effect on the body, a phenomenon now understood to be due to the inaction of androgens, and subsequent aromatization of testosterone into estrogen. A few years before Morris published his landmark paper,
Lawson Wilkins Lawson Wilkins (1894-1963) was a pioneering pediatric endocrinologist. He is known along with John Money for pioneering surgeries for visibly intersex newborns. Honors *Borden Award, American Academy of Pediatrics (1953) *Amory Prize, American A ...
had shown through experiment that unresponsiveness of the target cell to the action of androgenic hormones was a cause of "male pseudohermaphroditism". Wilkins' work, which clearly demonstrated the lack of a therapeutic effect when 46,XY patients were treated with androgens, caused a gradual shift in nomenclature from "testicular feminization" to "androgen resistance".


Other names

A distinct name has been given to many of the various presentations of AIS, such as Reifenstein syndrome (1947), Goldberg-Maxwell syndrome (1948), Morris' syndrome (1953), Gilbert-Dreyfus syndrome (1957), Lub's syndrome (1959), "incomplete testicular feminization" (1963), Rosewater syndrome (1965), and Aiman's syndrome (1979). Since it was not understood that these different presentations were all caused by the same set of mutations in the androgen receptor gene, a unique name was given to each new combination of symptoms, resulting in a complicated stratification of seemingly disparate disorders. Over the last 60 years, as reports of strikingly different phenotypes were reported to occur even among members of the same family, and as steady progress was made towards the understanding of the underlying molecular pathogenesis of AIS, these disorders were found to be different phenotypic expressions of one syndrome caused by molecular defects in the androgen receptor gene. AIS is now the accepted terminology for the syndromes resulting from unresponsiveness of the target cell to the action of androgenic hormones. CAIS encompasses the phenotypes previously described by "testicular feminization", Morris' syndrome, and Goldberg-Maxwell syndrome; PAIS includes Reifenstein syndrome, Gilbert-Dreyfus syndrome, Lub's syndrome, "incomplete testicular feminization", and Rosewater syndrome; and MAIS includes Aiman's syndrome. The more virilized phenotypes of AIS have sometimes been described as "undervirilized male syndrome", "infertile male syndrome", "undervirilized fertile male syndrome", etc., before evidence was reported that these conditions were caused by mutations in the ''AR'' gene. These diagnoses were used to describe a variety of mild defects in virilization; as a result, the phenotypes of some men who have been diagnosed as such are better described by PAIS (e.g.
micropenis Micropenis is an unusually small penis. A common criterion is a dorsal (measured on top) penile length of at least 2.5 standard deviations smaller than the mean human penis size (stretched penile length less than 9.3 cm (3.67 in) in adults ...
,
hypospadias Hypospadias is a common variation in fetal development of the penis in which the urethra does not open from its usual location in the head of the penis. It is the second-most common birth abnormality of the male reproductive system, affecting ab ...
, and undescended testes), while others are better described by MAIS (e.g. isolated male infertility or gynecomastia).


Society and culture

In the film '' Orchids, My Intersex Adventure'', Phoebe Hart and her sister Bonnie Hart, both women with CAIS, documented their exploration of AIS and other intersex issues. Recording artist Dalea is a Hispanic-American Activist who is public about her CAIS. She has given interviews about her condition and founded Girl Comet, a non-profit diversity awareness and inspiration initiative. In 2017, fashion model
Hanne Gaby Odiele Hanne Gaby Odiele (born 8 October 1988) is a Belgian model. Early life Odiele was born on 8 October 1988 in Kortrijk, Belgium. They were born with an intersex condition called androgen insensitivity syndrome. As a child, Odiele underwent ...
disclosed that they were born with the intersex trait androgen insensitivity syndrome. As a child, they underwent medical procedures relating to the condition, which they said took place without their or their parents' informed consent. They were told about their intersex condition weeks before beginning their modelling career. In the 1991 Japanese horror novel ''Ring'' and its sequels, by Koji Suzuki (later adapted into Japanese, Korean, and American films), the central antagonist Sadako has this syndrome, as revealed by Dr Nagao when confronted by Ryuji and Asakawa. Sadako's condition is referred to by the earlier name "testicular feminisation syndrome". In season 2, episode 13 ("Skin Deep") of the TV series ''House'', the main patient's cancerous testicle is mistaken for an ovary due to the patient's undiscovered CAIS. In season 2 of the
MTV MTV (Originally an initialism of Music Television) is an American cable channel that launched on August 1, 1981. Based in New York City, it serves as the flagship property of the MTV Entertainment Group, part of Paramount Media Networks, a di ...
series ''Faking It'', a character has CAIS. The character, Lauren Cooper, played by
Bailey De Young Bailey Marie De Young (''née'' Buntain; September 16, 1989) is an American actress. She is known for playing Ginny Thompson on ''Bunheads'', Lauren Cooper on '' Faking It'', and Imogene Cleary on '' The Marvelous Mrs. Maisel''. Career De Y ...
, was the first intersex series regular on American television. In season 8, episode 11 ("Delko for the Defense") of the TV series ''CSI: Miami'', the primary suspect has AIS which gets him off a rape charge. In series 8, episode 5 of '' Call the Midwife'', a woman discovers that she has AIS. She attends a cervical smear and brings up that she has never had a period, and is concerned about having children as she is about to be married. She is then diagnosed with "testicular feminisation syndrome", the old term for AIS.


People with AIS

*
Kitty Anderson (activist) Kitty Anderson is an intersex activist from Iceland. She is a co-chair of European intersex organization OII Europe, a co-founder of Intersex Iceland, and chairman of the board of the Icelandic Human Rights Centre. She has been described as a ...
*
Eden Atwood Eden Atwood is an American jazz singer and actress. She is the daughter of composer Hubbard Atwood and the granddaughter of the novelist A. B. Guthrie Jr. Career Atwood was born in Memphis, Tennessee. When she was five, her parents got a divor ...
* Bonnie Hart * Phoebe Hart *
Maria José Martínez-Patiño Maria José Martínez-Patiño (born 10 July 1961) is a Spanish former hurdler, whose dismissal from the Spanish Olympic team in 1986 for failing the gender test is a notable moment in the history of sex verification in sports. Martínez-Patiño wa ...
*
Hanne Gaby Odiele Hanne Gaby Odiele (born 8 October 1988) is a Belgian model. Early life Odiele was born on 8 October 1988 in Kortrijk, Belgium. They were born with an intersex condition called androgen insensitivity syndrome. As a child, Odiele underwent ...
* Santhi Soundarajan *
Miriam van der Have Miriam van der Have is an intersex human rights activist and woman with androgen insensitivity syndrome. She is a co-founder and co-chair of OII Europe e.V in 2015, co-founder and managing director of NNID Foundation in the Netherlands and memb ...
* Kimberly Zieselman


People with Complete androgen insensitivity syndrome

* Georgiann Davis * Seven Graham


People with Partial androgen insensitivity syndrome

* Tony Briffa * Favorinus of Arelate has been described as having partial androgen insensitivity syndrome. * Small Luk *
Eliana Rubashkyn Eliana Rubashkyn (; ), (born 25 June 1988) is a New Zealand pharmacist and chemist, known for being the first intersex person assigned male at birth legally recognised as a woman with a UN mechanism under the international refugee statute. Born ...
* Sean Saifa Wall * Sogto Ochirov


See also

* Estrogen insensitivity syndrome * Spinal and bulbar muscular atrophy *
Congenital adrenal hyperplasia Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders characterized by impaired cortisol synthesis. It results from the deficiency of one of the five enzymes required for the synthesis of cortisol in the adrenal cortex ...
*
5α-Reductase 2 deficiency 5α-Reductase 2 deficiency (5αR2D) is an autosomal recessive condition caused by a mutation in ''SRD5A2'', a gene encoding the enzyme 5α-reductase type 2 (5αR2). The condition is rare, affects only genetic males, and has a broad spectrum o ...


References


External links


Information

* * , {{DEFAULTSORT:Androgen Insensitivity Syndrome Transcription factor deficiencies Syndromes affecting the endocrine system Endocrine gonad disorders Syndromes with tumors Intersex variations