This document discusses sexual development and disorders of sex development (DSDs). It begins with an introduction that defines DSDs and provides background on their incidence, causes, and challenges in management. It then covers the physiology of typical male and female sexual differentiation, including development of the gonads, genital ducts, and external genitalia. Key control genes and pathways involved in testis formation like SRY and SOX9 are described, as well as those involved in ovary formation such as WNT4, RSPO1, and FOXL2. The roles of hormones like AMH, testosterone, and their receptors are also summarized.
2. CONTENT
Introduction
Development
Physiology
Male differentiation
Female differentiation
Classification
Sex chromosome DSD
46XY DSD
46XX DSD
2
3. INTRODUCTION
A disorder of sex development (DSD) is defined as a
congenital condition in which development of chromosomal,
gonadal, or anatomical sex is atypical
DSDs occur with an incidence of 1:4,500 to 1:5,000 live births
Phenotypic sex results from the differentiation of internal ducts
and external genitalia under the influence of sex-determining
genes and hormones
DSDs are a very important clinical issue with its different
aspects relating to diagnosis, treatment and sex of rearing
3
4. INTRODUCTION…
DSDs are always challenging to manage
Choosing the optimal gender is difficult when the genitalia are
ambiguous
Genital surgery is often required and both the type and the
timing of surgery raise controversial issues
Underlying endocrine disturbances are present in most cases
and usually require long term medication
4
Thuyen U, Lanz K, Holterhus PM, Hiort O. Epidemiology and initial management of ambiguous genitalia
at birth in Germany. Horm Res 2006;66:195–203
5. INTRODUCTION…
Fertility is impaired in nearly all DSDs
Gonadal development is impaired in most cases & is
associated with increased risk of neoplasia
There is the risk that childhood and adolescence for affected
individuals will be compromised by gender dysphoria and
other psychosexual difficulties, which may carry over into adult
life
5
6. The gonads derive from three sources
The mesothelium
Mesodermal epithelium lining the posterior abdominal wall.
The mesenchyme
Underlying connective tissue.
The primordial germ cells.
The initial stage is same in both sexes.
Called as stage of indifferent gonads.
Keith L. Moore, The Developing Human: Clinically Oriented Embryology, development of urogenital system, Elsevier , pp 274-336
8. Fifth week.
Thickened area of
mesothelium develops on
the medial wall of the
mesonephrons.
Underlying mesenchyme
proliferates.
Gonadal ridge.
Keith L. Moore, The Developing Human: Clinically Oriented Embryology, development of urogenital system, Elsevier , pp 274-336
9. Finger like epithelial cords grow into the
mesenchyme
Gonadal cords.
Gonad now consists of
Cortex
Forms the ovary.
Regresses in males.
Medulla
Forms the testis.
Regresses in females.
Keith L. Moore, The Developing Human: Clinically Oriented Embryology, development of urogenital system, Elsevier , pp 274-336
10. PRIMORDIAL GERM CELLS
Endodermal cells of yolk sac.
Near the origin of allantois.
They migrate along the dorsal mesentry and are
incorporated into the embryo.
Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
12. TESTIS
A dense layer of fibrous connective tissue
separates the testis cords from the surface
epithelium:- Tunica albuginea
Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
13. Testis cords are composed of
Primitive germ cells.
Sustentacular cells of Sertoli derived from the surface
epithelium of the gland.
Interstitial cells of Leydig derived from the original
mesenchyme.
Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
14. DESCENT OF TESTIS
The testis develop in the abdomen.
They descend into the scrotum which is a favorable
environment for sperm production.
Inguinal canal contracts after
they enter the scrotum
Heyns CF, Hutson JM. Historical review of theories on testicular descent. J Urol. 1995;153:754-67.
15. 5-8 wk processus vaginalis
Gubernaculum attaches to lower epididymis
12 wk to 7th month
Transabdominal descent to internal inguinal ring.
8th month
Inguinal canal.
9th month
Scrotum.
Heyns CF, Hutson JM. Historical review of theories on testicular descent. J Urol. 1995;153:754-67.
16. OVARY
The germ cells in the degenerating medullary sex
cords invade the cortical sex cords.
Germ cells differentiate into oogonia and enter 1st
meiosis - then arrest.
Cords break up into cell clusters
Primitive follicles containing oogonia and follicle cells.
Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
17. The surface epithelium becomes separated from
the follicles in the cortex by a thin fibrous capsule
The tunica albuginea.
The ovary separates from the developing
mesonephrons.
Suspended by a mesentey
The mesovarium.
Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
18. Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
20. FEMALE
In the absence of testosterone
The mesonephric duct degenerates.
The Mullerian duct develops uninhibited.
Mullerian duct
Cranial funnel-shaped opening to the coelom.
Forms the fimbriare of the infundibulum.
Keith L. Moore, The Developing Human: Clinically Oriented Embryology, development of urogenital system, Elsevier , pp 274-336
21. The cranial Mullerian duct forms the uterine tubes.
The caudal end of the Mullerian ducts fuse to form
the
Uterovaginal canal that later forms the uterus.
The superior vagina.
Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
22. Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
23. MALE
The male ductal system develops from the
mesonephric ducts while the paramesonephric
(Mullerian) duct degenerates.
Keith L. Moore, The Developing Human: Clinically Oriented Embryology, development of urogenital system, Elsevier , pp 274-336
25. Mesodermal cells form rudiments of external genitalia.
Genital folds flank the urogenital membrane.
The anterior genital folds forms the genital tubercle.
Lateral to the genital folds are the genital swellings.
The genital tubercle elongates to form the phallus.
Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
26. Male development
Phallus elongates.
Genital swellings enlarge and fuse to form the scrotum.
Genital folds fuse to form the penile urethra.
Female development
Phallus bends inferiorly- becomes clitoris.
Urethral folds- labia minora.
Labioscrotal folds- labia majora.
Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
27. Sadler, T W (Thomas W); Langman, Jan. Medical embryology. 12th ed. Philadelphia : Wolters Kluwer Health/Lippincott Williams &
Wilkins, c2012., pp321-355
29. PHYSIOLOGY
Sex determination is the result of a series of
molecular events that direct the
undifferentiated bipotential gonad to become
either a testis or an ovary
The bipotential gonad develops from the
urogenital ridge
By 6-7 weeks of fetal life, fetuses of both
sexes have two sets of internal ducts:
the Müllerian ducts and
the Wolffian ducts
The external genitalia at 6-7 weeks
gestation appear female and include a
genital tubercle, the genital folds, urethral
folds and a urogenital opening
29
31. PHYSIOLOGY…
During the bipotential stage, many genes (WT1, SF1, LHX9,
LIM1, PAX2, GATA4, EMX2, WNT4) are expressed at similarly
low levels in XY and XX gonadal ridges
However, all are necessary for normal gonadal development
in both sexes, with gene dosage and relative expression
levels playing an important role in the sexually divergent fate
of the gonads
The steroidogenic factor 1 (SF1), Wingless-type gene
(WNT4) and Wilms tumor suppressor gene 1 (WT1) are
expressed in the urogenital ridge and have a role in the
formation of the gonads, kidneys and adrenal cortex
31
32. PHYSIOLOGY…
The important event in gonadal differentiation is the commitment
of the bipotential gonad to become either an ovary or a testis
The essential genes affecting this process are as follows: WT1,
SF1,CBX2, SOX9, fibroblast growth factor 9 (FGF9),
prostaglandin D2 (PGD2), DAX1, WNT4, forkhead family
transcription factor 2 (FOXL2), R-Spondin 1 (RSPO1) and β-
catenin
While SOX9, FGF9 and PGD2 have more testis-promoting
activity, DAX1, WNT4, FOXL2, RSPO1 and β-catenin are
predominantly ovary-promoting genes
SOX9/FGF9 and WNT4/RSPO1 act as antagonistic signals in
early gonadal differentiation 32
Houmart B, Small C, Yang L, Naluai–Cecchinit, Cheng E, Hassold T, Griswold M. Global gene
expression in human fetal testis or ovary. Biol Reproduct 2009;81:438-443.
33. PHYSIOLOGY…
Male differentiation:
Male phenotypic development can be viewed as a two-step
process:
1. testis formation from the primitive gonad (sexual determination)
and
2. internal and external genitalia differentiation by action of hormones
secreted by the fetal testis (sexual differentiation)
Testis determination occurs at about the sixth week of
gestation
33
MacLaughlin DT, Donahoe PK. Sex determination and differentiation.
N Engl J Med 2004;350:367-378.
34. PHYSIOLOGY…
Male differentiation…
34
2. Expression of several genes
including WT1,CBX2(M33), SF1,
GATA4/FOG2 is critical to SRY
activation
3. The SRY gene encodes a unique
transcription factor that activates a
testis-forming pathway
4. After expression of SRY, SOX9
expression is up-regulated in the
developing testis
5. The SOX9 gene is essential for early
testis development which up-
regulates PGD2 & FGF9 genes
6. FGF9 & PGD2 maintain SOX9
expression, forming a positive feed-
forward loop in XY gonads
1. SRY gene that is located on the Y-
chromosome initiates sex
determination by downstream
regulation of sex-determining factors
35. PHYSIOLOGY…
Male differentiation…
Anti-müllerian hormone (AMH) acts on its receptor in the Müllerian
ducts to cause their regression
Testosterone (T) acts on the androgen receptor (AR) in the Wolffian
ducts to induce the formation of epidydimis, deferent ducts and
seminal vesicles
The Leydig cells also produce insulin-like factor 3 (INSL3, relaxin-like
factor), which causes the testes to descend to the scrotum
T is further reduced to dihydrotestosterone (DHT), which acts on the
androgen receptor of the prostate and external genitalia to cause its
masculinization 35
36. PHYSIOLOGY…
Female differentiation:
36
1. DAX1 is necessary for both testicular
& ovarian development, with a need
for precise gene expression dosage
2. Overexpression in either DAX1 or
WNT4/RSPO1 antagonizes testis
formation
3. WNT4/RSPO1/β-catenin pathway
blocks FGF9 & promotes the ovarian
fate
4. In XX gonads, WNT4 dominates and
results in an induction of β-catenin &
silencing of FGF9 and SOX9
5. WNT4-signaling pathway plays a
major role in ovarian development &
maintenance, regulation of Müllerian
ducts formation & ovarian
steroidogenesis
1. In the absence of SRY, the support
cell precursors differentiate as
granulosa cells, thus initiating the
ovarian pathway
37. PHYSIOLOGY…
Female differentiation…
WNT4:
It has been shown to play a critical role in the development of
the reproductive system & also in the formation of the
kidneys, adrenals, pituitary gland, and mammary tissues
Absence of WNT4 leads to testis-like development within the
ovary
Conversely, overexpression of WNT4 in the male leads to
female sex reversal
37
Biason-Lauber A: WNT4 and R-Spontin1 signalling in ovarian development. Highlights.
46th Meeting ESPE, 2010, Praque.
38. PHYSIOLOGY…
Female differentiation…
RSPO1:
It is another gene essential in sex determination responsible
for the protein RSPO1, which plays an important role in
suppression of the SOX9 gene
Loss of function mutations in the human RSPO1 gene in mice
results in the formation of ovotestes in the XX fetus
WNT4, RSPO1 and β-catenin seem to have both pro-
ovarian and anti-testicular activities from early embryonic life
38
39. PHYSIOLOGY…
Female differentiation…
FOXL2 :
It may also have similar actions but postnatally
FOXL2 is expressed early within the genital ridge of the fetal,
postnatal and adult ovary and eyelids
FOXL2 is involved in granulosa cell differentiation, follicle
development and maintenance during fertile life
39
Ottolenghi C, Omari S, Garcia-Ortis JE, Uda M, Crisponi L, Foraboska A, Pilia G, Schlessinger D.
FOXL2 is required for commitment to ovary differentiation. Hum Mol Genet 2005;14:205
40. PHYSIOLOGY…
Female differentiation…
Müllerian ducts give rise to the fallopian tubes, uterus and the
upper two-third of the vagina
In the female, the genital tubercle becomes the clitoris, the
labio-scrotal folds become the labia majora, and the urethral
folds become the labia minora
40
42. CLASSIFICATION
The Lawson Wilkins Pediatric Endocrine Society (LWPES)
and the European Society for Paediatric Endocrinology
(ESPE) consensus group proposed the classification of DSDs
into:
1. Sex chromosome DSDs (45,X Turner and variants, 47,XXY
Klinefelter and variants, 45X/46XY mixed gonadal disgenesis
(MGD) and chromosomal ovotesticular DSD “46XX/46XY
chimeric type or mosaic type”);
2. 46,XY DSDs (disorders of testicular development or
disorders in androgen synthesis/action); and
3. 46,XX DSDs (disorders of ovarian development or fetal
androgen excess)
42
43. SEX CHROMOSOME DSDS
This type of DSDs is associated with a numerical sex
chromosome abnormality leading to abnormal gonadal
development
Sex chromosome DSD was formerly termed as gonadal
dysgenesis in most of the patients in this group
If a testis is poorly formed, it is called a dysgenetic testis, and
if an ovary is poorly formed, it is called a streak gonad
A patient with a Y chromosome is at high risk of developing a
tumor in a streak or dysgenetic gonad
43
44. SEX CHROMOSOME DSDS…
Klinefelter and Turner syndromes (TS) are the most frequently
encountered sex chromosomal abnormalities
More than half of girls with TS have chromosomal mosaicism
The most common genotype of Klinefelter syndrome is XXY,
although variants exist with different numbers of X
chromosome
44
Lee PA, Houk CP, Ahmet F, Hughes IA, and in collaboration with participants in the international
consensus conference on intersex organized by the Lawson Wilkinns
Pediatric Endocrine Society and the European Society for Pediatric Endocrinology.
Consensus statement on management of intersex disorders.
Pediatrics 2006;118:488-500.
45. SEX CHROMOSOME DSDS…
45X/46XY MGD:
The most common feature of MGD is asymmetric
development of the testes, often with a dysgenetic testis on
one side and a streak gonad on the other
Asymmetrical external and internal genitalia may also be
present
The presence of 45,X cell lines is frequently associated with
Y chromosome rearrangements (commonly dicentric and ring
Y chromosomes), which may also have an impact on the
phenotype 45
46. SEX CHROMOSOME DSDS…
Chromosomal ovotesticular DSD (chimeric type or mosaic
type):
It is associated with ovarian and testicular tissues found in
either the same or opposite gonad just as in 46,XX and 46,XY
ovotesticular DSD
The genital duct develops according to the ipsilateral gonad
46
47. 46,XY DSD
Male pseudohermaphrodite
46,XY DSD can result either from disorders of testicular
development or disorders in androgen synthesis/androgen
action
Male gonad(s) are palpable in the majority of 46,XY DSD
patients
Abnormalities in the expression of genes involved in the
cascade of testis determination can cause anomalies of
gonadal development
47
Damian D, Paulo S. Disorder of sexual development: Still a
big challenge. J Pediatr Endocrinol Metab 2007;20:749-50
48. 46,XY DSD…
Failure of testis determination results in the development of the
female phenotype
While genetic alterations resulting in partial testicular
development can give rise to a wide spectrum of incomplete
masculinization
Mutation in WT1 gene results in Denys-Drash syndrome
(without uterus) or Frasier syndrome (with uterus) characterized
by 46,XY partial gonadal dysgenesis & severe renal dysfunction
with or without Wilms tumor
Complete gonadal dysgenesis in 46,XY individuals (Swyer
syndrome) is characterized by a female phenotype with full
development of unambiguous female genitalia, normally
developed Müllerian structures, & streak gonads
48
49. 46,XX DSD
Female pseudohermaphrodite
46,XX DSD can result either from disorders of ovarian
development or fetal androgen excess
SRY positivity; WNT4, RSPO1, β−catenin gene defects; and
duplication of SOX9 gene lead to testis-like formation within
the ovary (streak gonad, dysgenetic testis or ovotestis) in the
46,XX patients
A single copy of the WNT4 gene in females causes Müllerian
abnormalities, renal abnormalies (e.g. renal agenesis), and
androgen excess 49
50. 46,XX DSD…
With absence of both copies of WNT4 gene, females show
male sex and SERKAL syndrome (female to male sex
reversal; renal, adrenal and lung dysgenesis)
RSPO1 gene mutations lead to XX sex reversal,
palmoplantar hyperkeratosis and predisposition to squamous
cell carcinoma of the skin
Mutations in FOXL2 are responsible for blepharophimosis-
ptosis-epicanthus inversus syndrome (BPES) and can be
associated with premature ovarian failure
Ovarian dysgenesis coexisting with sensorineural deafness is
diagnosed as Perrault syndrome.
50
51. 46,XX DSD…
The majority of virilized 46,XX infants willhave congenital
adrenal hyperplasia (CAH) (most commonly 21α-hydroxylase
and 11β- hydroxylase or rarely 3β-hydroxysteroid
dehydrogenase deficiencies)
Mutations of POR gene cause disordered steroidogenesis
with prenatal virilization without worsening of postnatal
virilization in female fetuses
Rarer causes of fetal androgen excess in XX infants are
maternal androgen ingestion, maternal virilizing disease,
fetoplacental aromatase deficiency, sulfatase deficiency,
virilizing luteoma of pregnancy, glucocorticoid receptor
mutation 51
Damian D, Paulo S. Disorder of sexual development: Still a
big challenge. J Pediatr Endocrinol Metab 2007;20:749-50