Prenatal Sexual Differentiation

Everything you need to know about Prenatal Sexual Differentiation broken down into notes for you.

Prenatal Sexual Differentiation

Everything You Need to Know About Hormones….

  • Hormones: powerful chemical substances produced by endocrine glands
    • chemical messengers
  • Hormones have 2 kinds of effects:
    • Organizing Effects: prenatal sexual differentiation
    • Activating Effects: triggers the changes of puberty


Sex Hormones

  • The female hormones
    • estrogens: female sex hormone
    • progesterones: support pregnancy
  • Androgens: most notably testosterone
    • The “male” sex hormone

The Glands Involved

  • MANY endocrine glands
  • Pituitary Gland
    • the “master gland”
    • anterior lobe interacts with gonads.
    • Regulates hormone production
  • Hypothalamus
    • at base of brain
    • regulates the pituitary

Pituitary Hormones

  • Hypothalamus releases GnRH (Gonad Releasing Hormone)
  • Pituitary releases
    • Follicle Stimulating Hormone (FSH): controls spermatogenesis in males; stimulates follicles (containing eggs) in females
    • Luteinizing Hormone (LH): controls testosterone production in males; controls estrogen production in females

Prenatal Sexual Differentiation

  • In seventh week after conception, the sex chromosomes direct the gonads to begin differentiation
    • XX => female => ovaries
    • XY => male => testes
  • Female development is the default
    • At 7th week, testes start to form.
    • If no testes by 10-11 weeks, become ovaries


Ending up with a reproductively capable male is much harder than you might think:

  • XY
  • Testis Determining Factor (TDF) gene
  • Gonads differentiate into testes
  • Anti-Mullerian Hormone (AMH) (internal development)
  • Testosterone production
  • Body must respond to testosterone (external development)


Congenital Anomalies

Androgen Insensitivity Syndrome:

  • XY
  • non-functional internal male structures
  • external female development


Congenital Adrenal Hyperplasia (CAH)

  • Internal female. Fully functional.
  • Adrenal gland overproduces androgens prenatally
  • External development may be ambiguous
    • clitoris is often enlarged
    • labia may be partially fused
  • Tend to be tomboys
  • NOT RELATED TO HOMOSEXUALITY: they are heterosexual


  • People who have gender-determining biological variables that conflict
    • chromosomes
    • gonads
    • prenatal hormones
    • prenatal brain hormonalization
    • internal organs
    • external genital appearance
    • pubertal hormones

Sex Chromosome Abnormalities

  • XO Turner’s Syndrome
    • sterile
    • short and stumpy
  • XXY (Klinefelter’s)
    • Poorly developed secondary sexual characteristics and small testes
    • infertile, usually tall, and effeminate
    • may have subnormal intelligence
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5 Responses to “Prenatal Sexual Differentiation”
  1. Anuradha Ramkumar Says...

    On May 12, 2010 at 7:49 am

    Very informative article. Thnx for the wonderful share.

  2. mikky webs Says...

    On May 12, 2010 at 9:49 am


  3. jennifer eiffel01 Says...

    On May 12, 2010 at 7:40 pm

    Great article. Great explanation.

  4. VTech Says...

    On May 12, 2010 at 9:14 pm

    Very nicely written , Thanks for sharing.

  5. Aaron Hanlon Says...

    On May 14, 2010 at 6:44 am

    A well put together piece. Lots of info

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