Sexual Development.ppt

SEXUAL DEVELOPMENT AND ITS
DISORDERS

CONTENT
 Introduction
 Development
 Physiology
 Male differentiation
 Female differentiation
 Classification
 Sex chromosome DSD
 46XY DSD
 46XX DSD
2

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

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

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

 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

 Fifth week.
 Thickened area of
mesothelium develops on
the medial wall of the
mesonephrons.
 Underlying mesenchyme
proliferates.
 Gonadal ridge.

 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.

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

DEVELOPMENT OF TESTIS AND OVARY

TESTIS
 A dense layer of fibrous connective tissue
separates the testis cords from the surface
epithelium:- Tunica albuginea
Wilkins, c2012., pp321-355

 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.
Wilkins, c2012., pp321-355

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.

 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.

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.
Wilkins, c2012., pp321-355

 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.
Wilkins, c2012., pp321-355

Wilkins, c2012., pp321-355

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.

 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.
Wilkins, c2012., pp321-355

MALE
 The male ductal system develops from the
mesonephric ducts while the paramesonephric
(Mullerian) duct degenerates.

 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.
Wilkins, c2012., pp321-355

 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.
Wilkins, c2012., pp321-355

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

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

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.

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.

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

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

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

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.

PHYSIOLOGY…
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

PHYSIOLOGY…
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

PHYSIOLOGY…
 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

CLASSIFICATION
o Sex chromosome DSD
o 46X,Y DSD
o 46XX DSD

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

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

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.

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

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

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

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

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

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

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

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