Androgen Insensitivity Syndrome

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Androgen Insensitivity Syndrome
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• X-Linked Xq11-12
• 120,000-64,000 (rare)
• One of most common forms of male
  pseudohermaphroditism
• Normal androgen production and metabolism
• End-organ resistance to androgen action mainly
  due to defective androgen receptors.
• Mutations can be sporadic or familial (maternal
  carriers)
• 2 Forms
• Complete androgen insensitivity syndrome (CAIS)
• Partial androgen insensitivity syndrome (PAIS)

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• CLINICAL FEATURES
• CAIS
• Female habitus with normal female breast
  development
• Absence of pubic and axillary hair
• Female external genitalia underdeveloped labia,
  normal/small clitoris
• Blind-ending vaginas (often short)
• No male pattern of temporal balding
• Taller than average female height
• Internal genitalia Undescended aspermatogenic
  testes with normal testicular function (Leydig
  cell testosterone synthesis, Sertoli cell AMH
  synthesis)
• Absence of uterus and Fallopian tubes (Normal
  Müllerian structure regression)
• Majority raised as females

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• CLINICAL FEATURES
• PAIS
• Wide range of phenotypes
• Genital ambiguity - perineal hypospadias
• clitoromegaly/micropenis
• perineal orifice with labioscrotal folds
• bifid scrotum
• Normal male phenotype with infertility
  (oligo/azoospermia)
• Predominantly male external genitalia
• Female phenotype with sparse, scant pubic and
  axillary hair
• 59 raised as male

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CLINICAL FEATURES
A.
B.

• A. CAIS B. PAIS grade 3
  micro penis, hypospadal urethral orifice
  and bilateral cryptorchidism

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MOLECULAR ACTION OF ANDROGENS

• Testosterone diffuses into cell.
• Binds to intracellular androgen receptor
• Dissociation of heat shock protein on ligand
  binding
• Transport of ligand-receptor complex to nucleus
  through nuclear pores
• Binding of receptor complex to specific hormone
  response elements via DNA binding domain
• Binding of p160 family of co-factors and enzymes
• Transcriptional activation
• Expression of proteins in response to androgen

Neurological development
Male phenotype
Immunity
Maintenance of male phenotype
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• PATHOPHYSIOLOGY
• Mutation within androgen receptor
• Failure to bind to ligand
• Failure to bind to DNA
• Failure to form functioning androgen receptor
• Truncated proteins, mRNA splicing errors, Failure
  to fold into functioning 3D protein structure.
• Even with normal androgen production and
  metabolism no target organ response due to
  androgen receptor resistance.
• Unopposed oestrogen activity (testes and
  peripheral aromatisation) in utero and in vivo

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INVESTIGATIONS

• Presentation
• Child indirect inguinal hernia ambiguous
  genitalia
• PAIS mostly present in 1st month of
  life
• CAIS - median age 1 yr
• Testes palpable in 77 CAIS, 41 PAIS

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INVESTIGATIONS
Presentation Adolescent - Primary
amenorrhoea Adult - May be in denial of
abnormality of the years. Few sexual
relationships?
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INVESTIGATIONS
History 50 of CAIS have a positive family
history Important for genetic
counselling Indicates for family
screening Heterozygous 46,XX Females with
sparse, delayed asymmetric pubic or axillary
hair or delayed menarche (Carriers) Infertile
46,XY Maternal aunts or uncles
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EXAMINATION
B.
A.

• Classification system
• 1 least severe, 7 most severe
• External masculinisation score
• 12 normal male external genitalia

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INVESTIGATING PRESENCE OF Y CHROMOSOME

• Differentially diagnose genital ambiguity
• Peripheral leukocyte karyotyping
• Gold standard
• Array of metaphasic chromosomes
• 46,XY males vs
• 46, XX females (CAH)

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INVESTIGATING PRESENCE OF Y CHROMOSOME

• Fluorescence in situ
• hybridisation (FISH) with cDNA probes specific
  to X and Y chromatin.
• X Green signal
• Y Orange/red signal
• Quicker than karyotyping

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DIFFERENTIAL DIAGNOSES FOR MALE
PSEUDOHERMAPHRODITISM

• AIS
• XY gonadal dysgenesis (streak gonads)
• Testicular regression syndrome
• Leydig cell hypoplasia
• Enzymatic defects
• 5a-reductase deficiency
• 17a-hydroxylase deficiency

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IMAGING

• Ultrasound scanning for presence of uterus,
  ovaries (Müllerian)
• Ultrasound scanning for presence of testes if
  non-palpable (Transvaginal)
• MRI/LAPAROSCOPY If USS not useful
• Disadvantages Invasive, anaesthesia,
  children

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PRENATAL PELVIC ULTRASOUND

• When there is discrepancy between genotype and
  phenotype
• Useful for mothers with positive family history
• 22-24 wks will show abnormality

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HORMONAL ANALYSES
HORMONE OR PROTEIN NORMAL MALE REFERENCE VALUE AIS
LH 2 10 u/L Normal / ?
TESTOSTERONE 9 30 nmol/L Normal / ?
SHBG 13 71 nmol/L ? (female) 18 114 nmol/L
AMH (ADULT) 22 38 pmol/L ? 391 pmol/L
AMH (PREPUBERTAL) 251 679 pmol/L ? 1056 pmol/L
hCG STIMULATION TEST 3ng/ml 10ng/ml
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GONADAL BIOPSY

• Functioning testes
• Sertoli cell function normal (AMH production)
• Leydig cell function normal (T and E2)
• Absence of germ cells, aspermatogenic semniferous
  tubules

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GENITAL SKIN BIOPSY

• Highly sensitive to androgens
• Cultured fibroblasts
• Study androgen binding activity, to evaluate
  severity of AIS
• No binding CAIS

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DNA ANALYSIS

• Screen Families (Buccal smears, CAG repeats in
  exon 1)
• Prenatal screening 9-12 weeks by chorionic villus
  sampling of foetal side
• 16th week by ultrasound and amniocentesis
• Bloods taken from patient

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DNA ANALYSIS

• Northern Blots to assess AR mRNA expression
• PCR regions of DNA containing AR exons
• Failure to amplify regions suggests large
  deletions
• Denaturing gradient gel electrophoresis
• Single strand polymorphism analysis
• Automated DNA sequencing

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AR MUTATIONS

• Large deletions
• 1-4 base pair insertions / deletions
• Nonsense mutations (Premature termination stop
  codons)
• Missense Single amino acid substitutions (gt90)
• A given AR mutation can be causally related to
  AIS by recreating mutant in AR cDNA and
  demonstrating abnormality after transfection into
  AR-free host cells

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REFERENCES

• Ahmed SF, Cheng L, Dovey L, Hawkins JR, Martin H,
  Rowland J, Shimura N, Tait AD, Hughes IA.
  Phenotypic features, androgen receptor binding
  and mutational analysis in 278 clinical cases
  reported as AIS J Clin Endocrinol Metab
  200085(2)658-665
• www.androgendb.mcgill.ca
• www.medhelp.org/www/ais
• Turner HE, Wass JAH. Oxford handbook of
  Endocrinology and Diabetes. Oxford University
  Press 2003
• Quigley CA, De Bellis A, Marschke KB, El-Awady
  MK, Wilson EM, French FS. Androgen receptor
  defects Historical, clinical, and molecular
  perspectives Endocrin Rev 199516(3)271-321
• Gobinet J, Poujol N, Sultan C. Molecular action
  of androgens Mol Cell Endocrinol 200219815-24
• Ahmed SF, Hughes IA. The clinical asessment of
  intersex Curr Paed 200010269-274
• Pinhas-Hamiel O, Zalel Y, Smith E, Mazkareth R,
  Aviram A, Lipitz S, Achiron R. Prenatal diagnosis
  of sex differentiation disorders the role of
  fetal ultrasound J Clin Endocrinol Metab
  200287(10)4547-4553