Sex Determination

There are 2 types of sex chromosomes in humans: X and Y. Chromosomal sex is male when a Y chromosome is present (e.g., 46,XY or 47,XXY) and female when the Y chromosome is absent (e.g., 46,XX or 45,X0). Male phenotypes develop when a specific gene, called the SRY gene (usually found on the Y chromosome), is present, stimulating differentiation of the gonads into testes. The testes then produce testosterone (triggering development of the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis and scrotum externally and the ejaculatory system internally) and antimüllerian hormone (AMH), which causes regression of the müllerian ducts. Without the SRY gene, ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries develop; without testosterone, external female genitalia develop; and without AMH, the müllerian ducts persist and differentiate into the fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Posterior Abdominal Wall, uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall, and upper vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Table of Contents

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Overview

Definitions

The following definitions are relevant to the understanding of normal sex development:

  • Chromosomal sex (also referred to as genetic sex): the sex as defined by a person’s chromosomes:
    • Males: include a Y chromosome, typically 46,XY
    • Females: do not include a Y chromosome, typically 46,XX 
  • Gonadal sex: describes the type of gonads present within an individual
    • Males: testes
    • Females: ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries
    • Hermaphroditic gonads: ovotestis
  • Phenotypic sex: the appearance of the external genitalia (starting at birth) and secondary sex characteristics (at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty)
  • Sex determination: The process of transformation of the indifferent gonad into a testis or an ovary
  • Sex differentiation: Development of the phenotype as an expression of hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview produced by the specific gonads
  • Gender (sex) assignment: Designation of male or female gender at birth
  • Gender identity: the sense of self as being male or female
  • Sexual orientation: Refers to the target of sexual arousal and is independent of the person’s gender identity

Overview of typical sex development

  • Chromosomal sex → determines gonadal sex → determines phenotypic sex
  • Up until 6 weeks of gestation, sex development is identical and nonbinary; developing structures include:
    • Nonbinary, bipotent, undifferentiated gonads
    • Wolffian and müllerian ducts (both are present in both sexes initially)
    • Urogenital sinus
    • The genital tubercle, genital swellings, and genital folds 
  • The genes present at fertilization Fertilization To undergo fertilization, the sperm enters the uterus, travels towards the ampulla of the fallopian tube, and encounters the oocyte. The zona pellucida (the outer layer of the oocyte) deteriorates along with the zygote, which travels towards the uterus and eventually forms a blastocyst, allowing for implantation to occur. Fertilization and First Week will determine how the developing bipotent gonads differentiate (e.g., into a testis or an ovary)
  • The developing gonads will then secrete hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview.
    • The presence and/or absence of specific hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview will determine how the remaining structures differentiate.
    • In general, female organs and structures are the “default” phenotype if specific genes and hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview are not present to stimulate male differentiation.
  • Internal and external genital structures develop in response to hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview in utero.
  • Secondary sex characteristics develop in response to hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty.

Overview of genital structures

  • Gonads: develop based on the karyotype/genes present
    • Testes: 
      • Develop when sex-determining region of the Y chromosome (SRY gene) is present
      • Secrete testosterone and antimüllerian hormone (AMH)
    • Ovaries: develop when the SRY gene is absent 
    • Ovotestis: a gonad containing both ovarian and testicular tissue found in individuals with true hermaphroditism True hermaphroditism True hermaphroditism, or ovotesticular disorder of sexual development (ODSD), is characterized by the presence of an ovotesticular gonad that contains both ovarian and testicular elements. Individuals are usually born with ambiguous genitalia, but the diagnosis is rarely confirmed before puberty. The most common karyotype is 46,XX, and less often, 46,XY can be identified. True Hermaphroditism
  • Wolffian structures: differentiate from the wolffian (mesonephric) ducts in the presence of testosterone:
  • Müllerian structures: differentiate from the müllerian (paramesonephric) ducts when AMH is absent:
    • Uterus
    • Fallopian tubes
    • Upper vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor
  • External genitalia: develop from undifferentiated genital tubercle, genital swelling, and genital folds based on the presence or absence of testosterone
    • Male: testosterone 
      • Penis 
      • Scrotum
    • Female: lack of testosterone
      • Clitoris
      • Labia majora
      • Labia minora

Secondary sexual characteristics

Secondary sexual characteristics develop based on the hormonal milieu at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty.

  • Androgenic characteristics (i.e., “male”): due to the presence of testosterone and/or dihydrotestosterone (DHT):
    • Pubic and axillary hair
    • Facial and body hair in an androgenic distribution and quality (dark and coarse)
    • Deepening of the voice
    • ↑ Muscle mass
  • Estrogenic characteristics (i.e., “female”): due to the presence of estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries
    • Breast development
    • Wider hips

The Sex Chromosomes

There are 2 sex chromosomes in humans: X and Y.

Y chromosome

  • Approximately 58 million base pairs
  • Estimated to have 70–200 genes 
  • Acrocentric chromosome 
  • The Y chromosome is quintessentially the “sex-determining” chromosome   
    • Contains the SRY gene, which is key for male development
    • Y-linked traits are inherited from male to male only 
  • Pairs with the X chromosome during cell division
  • Pseudoautosomal region: 
    • An area on the short arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm of the Y chromosome that is homologous to a region on the short arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm of the X chromosome
    • Some crossing over between the X and Y chromosomes is possible at this location.
A male set of chromosomes

A male set of chromosomes:
The Y chromosome is highlighted.

Image: “Human male karyotpe high resolution – Chromosome Y” by National Human Genome Research Institute. License: Public Domain

X chromosome

  • Approximately 155 million base pairs
  • Estimated to have 800–900 genes 
  • Genetic disorders caused by mutations in genes on the X chromosome:
    • Called X-linked disorders
    • May be inherited in a dominant or recessive fashion
    • More often affect males, who have only 1 copy of the X chromosome
  • X-inactivation:
    • Also called lyonization
    • All X chromosomes except 1 are inactivated early in embryologic development in females:
      • In individuals with a 46,XX genotype, 1 X chromosome will be inactivated.
      • In individuals with a 47,XXY genotype, 2 X chromosomes will be inactivated.
    • The inactivated chromosome is compacted into heterochromatin, creating a structure known as a Barr body.
    • Partially responsible for the phenomenon known as dosage compensation, which is the reason why aneuploidies of the sex chromosomes have substantially smaller impacts on an individual than autosomal aneuploidies.
  • X chromosome aneuploidy is one of the most common chromosomal abnormalities.

The Genetics of Sex Determination

Typical male development

  • Male development starts because of the presence of the sex-determining region of the Y chromosome gene (SRY gene)
    • Located on the short arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm of the Y chromosome at Yp11.3
    • Produces a transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription factor called testis-determining factor (TDF), which is also known as the SRY protein 
  • TDF:
    • Alters the expression of multiple transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription factors, which trigger the differentiation of structures unique to the testes:
      • Sertoli cells
      • Leydig cells
      • Seminiferous tubules
    • Suppresses the expression of genes required for ovarian development:
      • Wnt4
      • R spondin 1 (Rspo1)
  • Sertoli cells secrete AMH: 
    • Also called müllerian-inhibiting substance (MIS) or müllerian-inhibiting factor (MIF)
    • AMH causes regression of paramesonephric (i.e., müllerian) ducts.
    • Without AMH, the paramesonephric ducts would differentiate into female structures (the fallopian tubes Fallopian tubes The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The fallopian tubes receive an ovum after ovulation and help move it and/or a fertilized embryo toward the uterus via ciliated cells lining the tubes and peristaltic movements of its smooth muscle. Posterior Abdominal Wall, uterus Uterus The uterus, cervix, and fallopian tubes are part of the internal female reproductive system. The uterus has a thick wall made of smooth muscle (the myometrium) and an inner mucosal layer (the endometrium). The most inferior portion of the uterus is the cervix, which connects the uterine cavity to the vagina. Posterior Abdominal Wall, and upper vagina Vagina The vagina is the female genital canal, extending from the vulva externally to the cervix uteri internally. The structures have sexual, reproductive, and urinary functions and a rich blood supply, mainly arising from the internal iliac artery. Vagina, Vulva, and Pelvic Floor).
  • Leydig cells secrete testosterone:
    • Stimulate differentiation of the wolffian/mesonephric ducts into:
    • Converted to DHT by 5α-reductase → stimulates development of:
      • The prostate Prostate The prostate is a gland in the male reproductive system. The gland surrounds the bladder neck and a portion of the urethra. The prostate is an exocrine gland that produces a weakly acidic secretion, which accounts for roughly 20% of the seminal fluid. Prostate and other Male Reproductive Glands from the urogenital sinus 
      • External male genitalia: penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis and scrotum
  • Key genes/proteins involved in the testicular differentiation:
    • SRY gene/TDF: 
      • Up-regulates an autosomal gene called SOX9
      • Suppresses the expression of genes required for ovarian development
    • SOX9:
      • Induces morphologic changes that are critical in the differentiation of Sertoli cells and seminiferous tubules from precursor cells
      • Binds the promoter region of the AMH gene → produces AMH
      • Along with TDF, SOX9 is considered essential for testes development
    • Steroidogenic factor 1 (SF1): works with SOX9 at the promoter region of the AMH gene to ↑ production of AMH in Sertoli cells
    • WT1: transcription Transcription Transcription of genetic information is the first step in gene expression. Transcription is the process by which DNA is used as a template to make mRNA. This process is divided into 3 stages: initiation, elongation, and termination. Stages of Transcription factor that works with SF-1 to further ↑ production of AMH
    • Desert hedgehog (DHH): produced in Sertoli cells to help stimulate the differentiation of Leydig cells
    • Dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 (DAX1): 
      • Represses SF1 → ↓ AMH production 
      • Located on the short arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm of the X chromosome

Typical female development

Differentiation and development of the müllerian ducts and external genitalia will proceed when testicular androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens and AMH are absent.

  • Development of the ovary from the bipotent gonad requires absence of SRY (preventing differentiation into testes).
  • Other key genes/proteins involved in female sex determination:
    • Autosomal genes that repress SOX9:
      • Wnt4
      • Rspo1
      • FOXL2
    • DAX1 
  • Without SOX9 and with DAX1:
    • ↓ AMH production allows for the müllerian ducts to persist and develop.
    • No Leydig cells → no testosterone → female external genitalia develop
  • Embryos develop in the “female hormonal environment” within their mother, so it is unclear whether hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview produced by the fetus are required for their embryologic development.
  • At puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty, estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries stimulates:
    • Breast development
    • Widening of the hips

Related videos

Clinical Relevance: Disorders of Sexual Development

  • Disorders of sexual development (DSDs) are a group of conditions characterized by atypical sexual development in an individual, which may involve abnormalities in the structure and/or function of the internal reproductive organs and/or external genitalia. 
  • Congenital adrenal hyperplasia Congenital adrenal hyperplasia Congenital adrenal hyperplasia (CAH) consists of a group of autosomal recessive disorders that cause a deficiency of an enzyme needed in cortisol, aldosterone, and androgen synthesis. The most common subform of CAH is 21-hydroxylase deficiency, followed by 11β-hydroxylase deficiency. Congenital Adrenal Hyperplasia: Increased formation of male sexual hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview ( androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens) with virilization of the external female genitals. Characterized by low levels of cortisol, high levels of ACTH, and adrenal hyperplasia.
  • Androgen insensitivity syndrome Androgen insensitivity syndrome Androgen insensitivity syndrome (AIS) is an X-linked recessive condition in which a genetic mutation affects the function of androgen receptors, resulting in complete (CAIS), partial (PAIS), or mild (MAIS) resistance to testosterone. All individuals with AIS have a 46,XY karyotype; however, phenotypes vary and include phenotypic female, virilized female, undervirilized male, and phenotypic male individuals. Androgen Insensitivity Syndrome (AIS): Mutations in the androgen receptors cause partial or complete resistance to testosterone. Genotypically, affected individuals have a 46,XY karyotype and testes present internally. Testosterone levels are elevated, and some of this testosterone is converted to estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries peripherally. Clinically, individuals with complete AIS will present with no sexual hair and have normal-appearing external female genitalia. Individuals are usually assigned female gender at birth and will present at puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty with amenorrhea.
  • Aromatase deficiency Aromatase deficiency Aromatase deficiency is a very rare genetic condition with autosomal recessive inheritance. Aromatase deficiency is characterized by congenital estrogen deprivation with increased levels of testosterone due to decreased levels of the aromatase enzyme. Aromatase Deficiency: results in an inability to convert testosterone to estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries, primarily causing virilization of the external genitalia in females.
  • 5α-reductase deficiency: autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritancedisorder that impairs conversion of testosterone to DHT, preventing full development of the external genitalia in males. This disorder results in ambiguous genitalia in 46,XY individuals at birth. 
  • Pure gonadal dysgenesis: results in nonfunctional gonads. In 46,XX individuals, pure gonadal dysgenesis presents with premature ovarian insufficiency (i.e., premature menopause Menopause Menopause is a physiologic process in women characterized by the permanent cessation of menstruation that occurs after the loss of ovarian activity. Menopause can only be diagnosed retrospectively, after 12 months without menstrual bleeding. Menopause) in otherwise normal-appearing females. In 46,XY individuals, the condition is known as Swyer syndrome Swyer syndrome Swyer syndrome is a disorder of sex development caused by a defect in the SRY gene on chromosome Y. The syndrome is characterized by complete testicular dysgenesis in an individual who has a 46,XY karyotype and is phenotypically female. Swyer Syndrome; without functional testes, testosterone and MIF are not produced, so individuals have external female genitalia and normal müllerian structures. Affected individuals present in adolescence with primary amenorrhea Primary Amenorrhea Primary amenorrhea is defined as the absence of menstruation in a girl by age 13 years in the absence of secondary sex characteristics or by the age of 15 years with the presence of secondary sex characteristics. Etiologies can originate in the hypothalamic-pituitary-ovarian (HPO) axis or from anatomic abnormalities in the uterus or vagina. Primary Amenorrhea and lack of all secondary sex characteristics.  
  • Klinefelter syndrome Klinefelter syndrome Klinefelter syndrome is a chromosomal aneuploidy characterized by the presence of 1 or more extra X chromosomes in a male karyotype, most commonly leading to karyotype 47,XXY. Klinefelter syndrome is associated with decreased levels of testosterone and is the most common cause of congenital hypogonadism. Klinefelter Syndrome: Chromosomal aneuploidy characterized by the existence of ≥ 1 extra X chromosomes in a male karyotype (e.g., 47,XXY or 48,XXXY). Symptoms are not usually observed during childhood. During adulthood, individuals are typically tall males who present with gynecomastia Gynecomastia Gynecomastia is a benign proliferation of male breast glandular ductal tissue, usually bilateral, caused by increased estrogen activity, decreased testosterone activity, or medications. The condition is common and physiological in neonates, adolescent boys, and elderly men. Gynecomastia and infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility related to hypogonadism Hypogonadism Hypogonadism is a condition characterized by reduced or no sex hormone production by the testes or ovaries. Hypogonadism can result from primary (hypergonadotropic) or secondary (hypogonadotropic) failure. Symptoms include infertility, increased risk of osteoporosis, erectile dysfunction, decreased libido, and regression (or absence) of secondary sexual characteristics. Hypogonadism. Educational difficulties are also common.
  • Turner syndrome Turner syndrome Turner syndrome is a genetic condition affecting women, in which 1 X chromosome is partly or completely missing. The classic result is the karyotype 45,XO with a female phenotype. Turner syndrome is associated with decreased sex hormone levels and is the most common cause of primary amenorrhea. Turner Syndrome: chromosomal aneuploidy characterized by the absence of an X chromosome in a female karyotype (e.g., 45,X0). Clinical manifestations include a characteristic phenotype (short stature, webbed neck, widely spaced nipples) and multiple anomalies usually involving the cardiac, renal, reproductive, skeletal, and lymphatic systems. Gonadal dysgenesis and infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility are likely.
  • True hermaphroditism: presence of an ovotesticular gonad that contains both ovarian and testicular elements. Affected individuals are usually born with ambiguous genitalia, and the internal structures depend on the adjacent gonadal tissue. The most common karyotype is 46,XX.

References

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  2. Bashamboo, A., & McElreavey, K. (2016). Mechanism of sex determination in humans: insights from disorders of sex development. Sex Dev 10, pp. 313–325. https://doi.org/10.1159/000452637
  3. Cotinot, C., Pailhoux, E., Jaubert, F., & Fellous, M. (2002). Molecular genetics of sex determination. Semin Reprod Med 20, pp. 157–168. https://doi.org/10.1055/s-2002-35380
  4. McClelland, K., Bowles, J., & Koopman, P. (2012). Male sex determination: insights into molecular mechanisms. Asian J Androl 14, pp. 164–171. https://doi.org/10.1038/aja.2011.169
  5. Hake, L., & O’Connor C. (2008). Genetic mechanisms of sex determination. Nature Education 1:25. https://www.nature.com/scitable/topicpage/genetic-mechanisms-of-sex-determination-314/ 
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  7. Hiort, O. (2021). Typical sex development. UpToDate. Retrieved October 15, 2021, from https://www.uptodate.com/contents/typical-sex-development 

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