REI Genetics

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REI Genetics

• Jennifer Swoboda, MD

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GENETICS IN REPRODUCTIVE ENDOCRINOLOGY AND
INFERTILITY

• When does an REI specialist use genetics?
• infertility work-up
• recurrent pregnancy loss
• ambiguous genitalia
• disorders of androgen excess, amenorrhea
• assisted reproduction
• preimplantation genetic diagnosis

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GENETIC BASIS OF NORMAL AND ABNORMAL MÜLLERIAN
DEVELOPMENT

• mammalian sexual differentiation controlled by
• both genetic and hormonal influences
• human gonad is bipotential

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GENETIC BASIS OF NORMAL AND ABNORMAL MÜLLERIAN
DEVELOPMENT

• testicular differentiation (TDF) ? testis
  (facultative role)
• Y MIH müllarian inhibiting
  substance production
• production of testosterone
  conversion to
  
• dihydrotestosterone end organ androgen
  receptors
• SRY sex-determining region (short arm of Y)
• MIH müllerian inhibiting substance (Müllerian
  duct regression, Wolfian duct differentiation)
• TDF Testis-determining factor is a 35kilobase
  pair (kbp) sequence on the SRY area of the
  Y chromosome

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INFLUENCE of SRY GENE

• SRY gene directs a cascade of gene activation and
  protein production
•  
• Absence of SRY human gonad becomes ovary 
• Absence of testis -- internal external female
  genitalia 
• Multiple autosomal genes also play a role in
• testicular differentiation

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• Phallus too large normal clitoris, too small for
  a normal penis. The opening at the base of the
  penis (urine exits) may be true urethra or
  pseudourethra at apex of fused labia. May be
  incompletely fused scrotum or fused labia.
• Now what?

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NEONATE WITH AMBIGUOUS GENITALIA

• definitive assignment of sex should be withheld,
  with reassurance
• careful physical exam for palpable gonads,
  phallus length, position of urethral meatus, is
  there a vagina or vaginal pouch or urogenital
  sinus, degree of labioscrotal fusion, any other
  somatic abnormalities (mixed gonadal dysgenesis)
• immediate labs serum electrolytes, 17a-OH
  progesterone and karyotype
• serum sample should be frozen for subsequent
  analysis of steroid intermediates

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GENETIC BASIS OF AMBIGUOUS GENITALIA

• virilization of genetic females
• (female pseudohermaphroditism)
• undermasculinization of genetic males
• (male pseudohermaphroditism)
• true hermaphroditism
• (presence of both ovarian and testicular tissue)
  

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ANATOMY OF AMBIGUOUS GENITALIA

• b fused labia form pseudourethral opening and
  cover both the true
• urethra meatus and the vagina introitus. c
  opening at the base of the
• phallus is a urethra with hypospadias testis may
  has descended ?partially
• fused scrotum or remained in the abdominal cavity
  or inguinal canal

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FEMALE PSEUDOHERMAPHRODITISM 46 (X,X)

• most common cause
• congenital adrenal hyperplasia
• vast majority is deficiency of 21-hydroxylase
• 11-hydroxylase and 3-hydroxysteroid dehydrogenase
  deficiency also occur

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VIRILIZATION IN CONGENITAL ADRENAL HYPERPLASIA

• A mild with minimal labial fusion B
  intermediate
• C most severe form with urethra opening at tip
  of phallus

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Aromatase
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FEMALE PSEUDOHERMAPHRODITISM 46 (X,X)

• salt wasting form of 21-hydroxylase deficiency
• is life-threatening
• 11-hydroxylase deficiency presents with
  hypertension
• masculinization 2 elevated androgenic precursors
• produced by the adrenal gland
• rarely, exogenous source (meds) or maternal
  theca-lutein cyst ? maternal/fetal virilization

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CONGENITAL ADRENAL HYPERPLASIA 21-hydroxylase
deficiency

• most common form of CAH
• AR inheritance, chromosome 6
• (most CAH)
• untreated adult female note short stature,
  masculinized habitus, lack of female secondary
  sexual development
• tx exogenous cortisol, ex. hydrocortisone
  10mg/day

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MALE PSEUDOHERMAPHRODITISM

• Genetic male 46 (X,Y) with inadequate production
  of testosterone or
• dihydrotestosterone or lack of androgen
  responsiveness in target tissues
• palpable gonad strongly suggests genetic male (Y
  chrom.) or rarely, true hermaphrodite
• ? 17a-hydroxylase ? hypertension, hypokalemia
• ? 5a-reductase ? AR condition, normal testes,
  impaired conversion
• to dihydrotestosterone ? severe external
  genitalia ambiguity
• labioscrotal fusion and a urogenital
  sinus, severe hypospadia,
• elevated TDHT levels, without
  intervention, virilize at puberty
• (raise female with early gonadectomy to
  avoid virilization or male with amb. genitalia
  virilizes intersex issues)

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MALE PSEUDOHERMAPHRODITISM

• androgen receptor gene mutation ? androgen
  insensitivity syndrome 
• partial function leads to highly variable
  external genitalia from phenotypic female to
  phenotypic male

• mixed gonadal dysgenesis (45,X/46,XY) varying
  degrees of genital ambiguity

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MALE PSEUDOHERMAPHRODITISMSwyer syndrome is
46,XY (female phenotype)

• may present as primary amenorrhea with elevated
  gonadotropins
• embryonic testicular regression, before or during
  internal/external genital differentiation
• timing of degen ?internal differentiation into
  Wolfian vs Mullerian
• usually infantile female phenotype
  internal/external genitalia, streak gonads lack
  of 2 sexual development
• early gonadectomy

• (early gonadoblastoma occurance)
• usually raised as female, supplement estrogen/
  progesterone to encourage female 2 sexual
  development

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TRUE HERMAPHRODITISM

• most common 46,XX
• 10 46,XY
• rare 46,XY/46,XX
• (thought to be fusion of 46,XY and 46,XX embryos
  into chimera)
• any mixture of ovary, testis, and ovotestis
  either unilateral or bilateral is possible, with
  ovarian tissue more functional

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GENETIC BASIS OF DISORDERS OF MÜLLARIAN
DEVELOPMENT

• presenting as gonadal dysgenesis
• primary amenorrhea
• delayed puberty
• primary or secondary amenorrhea
• (1-2 - consider with short stature)
• must exclude 45,X cell line because

• associated cardiac anomalies (40-50) and
• renal anomalies (30)
•  approx. ½ of woman with primary amenorrhea and
  
• hypergonadotropic hypogonadism have some
• X - chromosome abnormality

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GENETIC CAUSES OF DELAYED PUBERTY

• Müllerian anomalies usually present during the
• adolescent years as primary amenorrhea.
• Genetic influence in
• ESTROGENIZED (eugonadal) müllerian aplasia vs.
  AIS
• NON-ESTROGENIZED HYPOGONADOTROPIN (low FSH/LH)
• Kallmans, Prader-Willi-Lambert,
  Laurence-Moon-Biedl
• NON-ESTROGENIZED HYPERGONADOTROPIN (high
  FSH/LH)
• Turners pure gonadal dysgenesis

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ESTROGENIZED HYPOGONADOTROPIN (low FSH/LH)

• MÜLLERIAN APLASIA Mayer-Rokitansky-Küster-Haus
  er
• 46,XX with normal ovaries, tubes, uterine
  remnants
• fusion failure of müllarian anlagen during
  development
• absent vagina and uterus may have vaginal pouch
• examine for assc. skeletal abnormalities (11-50)
• usually clinical diagnosis
• abd/pelvic USG --gt midline uterine remnant
  ovaries
• r/o unilateral renal agenesis or single pelvic
  kidney
• serum testosterone normal female level
• pregnancy possible with oocyte retrieval and use
  of gestational carrier (surrogate)

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MÜLLERIAN AGENESIS

• Normal bladder and rectal anatomy. Space between
  bladder and rectum usually occupied by Müllerian
  structures made up of loose areolar tissue that
  extends up to level of peritoneal reflection.

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ESTROGENIZED HYPOGONADOTROPIN (low FSH/LH)

• ANDROGEN INSENSITIVITY SYNDROME
• 46,XY female phenotype gene on Xq11-12
  mutation of androgen receptor absence/scant pubic
  hair, absent vagina or vaginal pouch,
• XLR inheritance
• SRY ? normal testis development
• MIS ? absence of cervix/uterus and formation of
• blind vaginal pouch
• peripheral conversion of androgens ? estrogens ?
  breasts
• serum testosterone nearly normal male

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ESTROGENIZED HYPOGONADOTROPIN (low FSH/LH)

• ANDROGEN INSENSITIVITY
• SYNDROME
• recommended laparoscopic gonadectomy s/p breast
  dev.
• incomplete androgen insensitivity gives varying
  range of
• phenotype
• predominately female with some ambiguity of
  external genitalia
• predominately male with hypospadia, micropenis,
  or only impaired spermatogenesis
• when diagnosis made, investigate family members
  apparent sisters 13 chance of 46,XY female
  offspring of normal sister with 16 chance of
  46,XY (require gonadectomy)

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NON-ESTROGENIZED HYPOGONADOTROPIN (low FSH/LH)

• Prader-Willi-Lambert

• Laurence-Moon-Biedl Syndrome obesity, mental
• deficiency, poly and/or syndactyly, genital
  hypo-plasia /or hypogonadism, retinitis
  pigmentosa autosomal recessive

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NON-ESTROGENIZED HYPOGONADOTROPIN (low
FSH/LH)

• Prader-Willi-Lambert hypotonia, dev. delay,
  hyperphagia almond-shaped eyes
• paternal chromosome 15 deletion (q11q13)
• example of genetic imprinting unequal
  expression of
  maternal and paternal alleles
• Kallmans absence of GnRH producing neurons and
  olfactory defect, hypogonadism, cryptorchidism,
  /- assc. cleft lip/palate, /- cong. deafness
• 3 modes of transmission (XLR, AD and AR)
• X-linked most common as evidenced by
• 5-7 x increased frequency in males

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NON-ESTROGENIZED HYPERGONADOTROPIN (high
FSH/LH)

• Gonadal Dysgenesis
• spectrum of disorders with assc.
  hypergonadotropic hypogonadism
• present with delayed puberty, lack of 2 sexual
  develop-
• ment and primary or secondary amenorrhea
• Karyotypes range from 45,X or 46,X(delX) single
  cell line to mosaic and structurally abn. X
  chrom.
• Less common apparently normal 46,XY or 46,XX

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NON-ESTROGENIZED HYPERGONADOTROPIN (high
FSH/LH) TURNERS SYNDROME
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Turners Syndrome pure gonadal
dysgenesis

• Short stature, sexual infantilism, webbed neck,
  streak gonads
• Visceral anomalies coarctation of aorta,
  bicuspid aortic valves, and horseshoe kidney
• cystic hygroma or hand/feet lymphedema
• fewer than 3 of 45,X ? viable infant
• (most frequent karyotype in 1st trimester SAB)
• of viable female, 1/3 with single 45,X cell
  line
• majority exhibit chromosomal mosaicism (45,X )
• or structural abn. of X chromosome
• 45,X/46,XY mosiac to mixed gonadal dysgenesis
• adrenal androgens ?nl adrenarche but infantile
  breast dev.
• require estrogen replacement therapy /- GRH to
  maximize height

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NOONANs SYNDROME

• affects males females with normal chromosomes
  and normal gonad function
• female phenotype Turners-like with different
  cardiac malformations (pulmonary stenosis vs.
  aortic coarctation)
• male phenotype male Turners
• AD with variable expression

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GENETIC BASIS OF REPETITIVE PREGNANCY LOSS

• traditional definition 3 or more consecutive
  spontaneous pregnancy losses
• recent studies show 2 losses with similar risk
  pattern for future spontaneous ABs (recurrence
  risk age dpdt. and increases with age)
• RPL effects 1-2 reproductive age women
• structural abnormalities in parental chromosomes
  occur in 3-5 couples with RPL. Most common
  balanced trans-location (in female 2-31). Also
  robertsonian translocation and supernumerary
  chromosomes. Management includes prenatal
  diagnosis with amnio/CVS, donor gametes, PGD.

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PREIMPLANTATION GENETIC DIAGNOSIS

• the future is here
• complete mapping of the human genome (draft 1999)
• specific genetic alterations associated with an
  increasing number of inherited diseases, both
  rare and common, are being classified
• biomedical advances allow for increased access to
  preimplantation genetic diagnosis
•  Wilkins-Haug L, et al. Genetics in
  Obstetricians' Offices A Survey Study. Obstet
  Gyn
• 199993(5)642-647

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PRINCIPLES OF PREIMPLANTATION GENETIC DIAGNOSIS

• PGD requires patients to undergo IVF in order to
  have pre-embryos available for testing (oocyte
  retrieval insemination)
• prior to transfer, one or two cells called
  blastomeres are safely removed
• chromosome analysis via PGD-FISH (flourescent in
  situ hybrid-ization)
• specific gene analysis via PGD-PCR (polymerase
  chain reaction)

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PRINCIPLES OF PREIMPLANTATION GENETIC DIAGNOSIS

• In AMA, ability to become pregnant is unaffected,
  but oocyte quality is compromised. Decreased
  implantation rate hypothesized to reflect
  increased aneuploidy in oocytes.
• PGD for aneuploidy at with 8 chromosomes yielded
• increased implantation
• reduced spontaneous abortion
• decreased trisomic conception
• Preimplantation Genetic Diagnosis of Numerical
  and Structural Chromosome Abnormalities, Munne S,
  2002

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PRINCIPLES OF PREIMPLANTATION GENETIC DIAGNOSIS

• PGD is accurate and safe, with no deleterious
  pre- or post-implantation developmental effects
  (1000 cycles)
• evaluation of single gene defects
• application for any genetic disease presently
  diagnosed by prenatal diagnosis
• future application for late onset and complex
  disorders
• Preimplantation Diagnosis for Single Gene
  Defects, Verlinsky Y, Rechitsky S, Kuliev A, 2002

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REFERENCES

• Precis Reproductive Endocrinology, 2nd Ed. 2002
• Clinical Gynecologic Endocrinology and
  Infertility, 6th Ed. Speroff L, et al.
• Infertility, Contraception Reproductive
  Endocrinology, 2nd Ed. Mishell D, Davanaj V
• ACOG Technical Assessment, Genetics and Molecular
  Diagnostic Testing,
• Number 1, July 2002
• Genetics In Obstetrics Gynecology, 2nd Ed.,
  Simpson J, Golbus, M
• Textbook of Reproductive Medicine, Carr B,
  Blackwell R, 1993
• Advances in Infertility Treatment, 2002
  Conference, Filicori M

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