Infancy and Childhood: Gender Development

Infancy and Childhood Development

Introduction to Gender

  • Gender development involves multiple stages throughout human life, including prenatal factors, and culminates in adult gender identity.

Prenatal: Chromosomes at conception: Fetal gonads, Fetal hormones

Infancy and Childhood: Sex assignment at birth: Rearing of child boy/girl: Child’s own body image

Hormonal Changes:

Historical Context of Gender Understanding

  • Prior to 19th Century:

    • General ignorance on gender; lack of scholarly interest and few substantial case studies existed.

  • 1890s:

    • Classification of gender based on gonads. Possession of ovaries classified individuals as women regardless of their outward masculine appearance.

  • 1910:

    • Biopsies were established as definitive measures to determine functional ovaries/testes, although societal classification leaned towards perceived believability rather than biological fact.

  • 1950:

    • Wilkins and Money introduced the idea of 'sex normalizing' surgeries and hormonal treatments.

  • Post-1950:

    • Milton Diamond highlighted severe issues stemming from these practices, noting frequently adverse outcomes.

Biological Sex Variations

  • Intersexed Individuals:

    • Defined as possessing biological traits of both sexes.

    • Genital structures may range between penis and vagina.

    • The term "hermaphrodite" is outdated and deemed inaccurate.

    • Occurs in about 2% of live births (Blackless et al., 2000).

  • Conditions Leading to Biological Variations:

    • Congenital Adrenal Hyperplasia (CAH)

    • Swyer Syndrome

    • Complete/Partial Androgen Insensitivity Syndrome

    • 5-Alpha-Reductase Deficiency

    • Turner’s Syndrome

    • Klinefelter’s Syndrome

Biological Sexual Development

  • Carnegie Stages of Human Development:

    • Key stages range from Zygote (1 day) to week 8+ gestation, highlighting critical phases of development, including sexual differentiation.

  • Early Week Development:

    • By ~3 weeks, a primitive heart circulates embryonic blood.

    • By 5-6 weeks, undifferentiated genitalia form.

    • Both male and female embryos exhibit primitive external genitalia, undeveloped gonads, and two sets of primitive ducts: Mullerian (female) and Wolffian (male).

  • Default Development Pathway:

    • Both sexes resemble primitive female structure during the frist 6 weeks.

    • Most mammalian fetal tissues predominantly develop towards female unless interrupted by male hormones.

    • By the 7th week, genetic coding (XX for female, XY for male) directs sexual differentiation.

    • Presence of the Y chromosome activates the development of testes; absence leads to ovarian development around weeks 11-12.

Fetal Gonadal Development

  • Mullerian Ducts:

    • Develop into female sexual and reproductive organs unless inhibited by male hormones.

  • Wolffian Ducts:

    • Develop into male sexual and reproductive organs if male hormones are present.

Specific Biological Conditions

  • Congenital Adrenal Hyperplasia (CAH):

    • Results from an inherited recessive gene leading to cortisol production deficiency and overproduction of adrenal androgens.

    • Between weeks 9-13, excess androgens can cause genital ambiguity in female fetuses.

    • Affects both XX (female) and XY (male) individuals:

      • XX individuals may show increased masculine traits.

      • XY individuals generally follow a typical male developmental pattern.

Alfred Jost:

  • Default pathway of most fetal tissues in mammals is to develop in the female direction.

7th Week: Genetic Code (XX/XY) Asserts itself

  • Activity on the Y chromosome causes the testes to begin to differentiate.

  • If the Y chromosome is absent, the ovaries develop and begin to form LATER at 11-12.

Fetal Gonades

  • Mullerian Ducts:

    • Embryonic structures that develop into female sexual and reproductive organs unless inhibited by male hormones.

  • Wolffian Ducts

    • Embryonic structures that develop into male sexual and reproductive organs if male hormones are present.

Congenital Adrenal Hyperplasia

  • Inherited recessive gene resulting in a deficiency in the production of cortisol and the overproduction of adrenal androgens.

  • Between the 9th and 13th week of gestation, excessive androgens negatively affect the female fetus.

  • Gender ambiguity can result.

  • CAH can occur in XX and XY.

  • XY: Physical and psychological development follows a typical male pattern.

  • XX: become more physically and psychologically masculine.

    • At birth, genitals appear partially or completely masculine, although internally, female gonads are present.

  • Masculinization of the female CAH psyche:

    • Interest in boys’ toys (e.g., vehcles, military accessories) and disinterest in girl toys (e.g., dolls)

    • Drawings contain boy motifis (e.g., vehicles, mechanisms) rather than feminine (e..g, human, animals).

    • During adolescence prefer male activites (e.g., martial arts, angliing, looking after motorcylce.)

  • Masculinization of the female CAH psyche:

    • Particularly good spatial ability (targeting, maze task).

    • Less interst in being mothers

    • 5% identify with being male.

  • In terms of sexuality (CAH females):

    • Most report attraction to men.

    • Some studies find higher raes of same-sex attraction and bisexual orientaiton.

  • Controversial treametn with dexamethasone.

    • Potent synthetic steroid.

    • Administered almost as soon as mother is pregnant and before 7th week when humans start to differentitate into m/f.

10 Week Male

10 Week Female

Biological Sxual Development

  • Specific region on the Y chromonsomes important for directing sexual development: SRY

  • SRY gene: causes precursor cells in the embryo to develop into Sertoli cells (produce anti-Mullerian hormone) and Leydig cells (produce testosterone) which cause the gonads to develop into testes.

    • XY males lacking SRY develop as females (Swyer syndrome)

    • XX with a misallocated SRY develop as males.

Swyer Syndrome: XY Lacking SRY (Complete 46, XY Gonadal Dysgenesis)

  • 1 in 80,000 births

  • Genetic male (XY).

  • The body does not respond to testosterone during development.

  • Have gondal streaks instead of sex glands. Ovaries are replaced by functionless (fibrous) scar tissue. Consequently, do not produce sex hormones and do not undergo puberty.

  • Possible female genital appearance at birth (but with undescended testes and an unusually short vagina, and no cervix).

Case Study

  • 15-year-old primary amenorrhea.

  • Prescribed Estrogen and Progestrone whihc she stopped taking.

  • Married at 15. Shorter than husband but considerably taller at age 50.

Swyer’s Advocate:

  • Sara Forsberg

Complete Androgen Insensitivity Syndrome

  • XY fetus insenstive ot production of its own androgens.

  • Despite XY, the body and genitals have a feminine genital appearance.

  • The child appears typical female with a shallow vagina.

  • Usually not detected until puberty, a failure to menstruate or underdeveloped testicles appears as a mass in the groin or abdomen.

  • Usually raised as girls and adopt a female gender identity.

  • Most becomes sexually active, and the majority are attracted to men.

Similarities/Differences

Swyer:

  • Little or no breast development.

  • Testes are replaced by fibrous streaks that don’t secrete testosterone.

CAIS:

  • Normal breast development.

  • Testes ar eusually well formed and located in the labia or abdomen.

  • Presence of testis-like masses in a phenotypically female suggests the diagnosis.

ASI Variant Hanne Gaby Odiele:

  • Born with XY chromosomes and had internal testes surgically removed as a child.

  • Identifies as intersex and non-binary.

  • Underwent surgery at 18 to reconstruct the vagina.

Partial Androgen Insensitivity Syndrome

  • XY male that partially responds to androgens.

  • Gentials appear to be a mix of male and female structures and not clearly identifiable.

  • Hypospadias (urethral opening on the underside of the corona).

  • Can identify as male or female

  • Sexual attraction is variable.

5-Alpha-Rductase-Deficiency

  • XY male fetus is unable to convert testosterone to dihydrotestosterone (DHT) due to insufficient levels of 5-alpha reductase enzyme.

  • DHT is necessary for the development of male external genital structures.

  • Depending on the amount of feministion they may appear completely female, a mix of male/female structures or incomplete male.

  • Regardless of external appearanc emale gonads are present internally.

  • Most 5-alphaRD babies raised as girls and adopt female gender identity during childhood.

  • But, upon reaching puberty, testosterone production results in masculinization.

    • Testes descend, genital sturcutre grow into a small penis, and secondary sex characteristics.

  • Most then switch to male gender identity. Those who do, are typically attracted to women.

Turner Syndrome (XO)

  • Prevalence: 1/2,500 females births

    • Female genitalia

    • Lack of ovaries, menstruation, pubic hair, and breasts with widely spaced nipples.

    • Stunted growth.

    • Treatemetn include growth hormones and hormonal replacement therapy

    • Most identify as female.

Dichotic Listening Task:

  • Most people have a left hemisphere dominance for verbal listening.

Finger Print Ridge Count:

  • Low ridge count signifies a slower cell division rate during gestation and results in a smaller left hemisphere development.

  • Hence, the language deficits are in Klinefelter’s but not Turner’s.

  • Lower ridege count associated with worse verbal ability.

Dr. C. Netlet Supported 30 Years Later With fMRI

Developments…Less Common

  • Supernumery Y Syndrome (XYY)

    • Appearance of a normal male

    • Tend to be taller stature

    • Some lack of control over impulses

    • Usually average intelligence.

  • Triple X Syndrome (XXX)

    • Appearance of a normal female

    • Sometimes infertile

    • Occasional intellectual impairment.

Biological Sexual Development

  • Possible True Hermaphrodite (XX/XY)

  • Exceptionally rare, 5% or less of all intersex conditions. Often reported only in case studies.

  • Variable. A combination of ovarian and testicular tissue.

  • Usually have a uterus.

  • At puberty, most experience breast enlargement and the majority menstruate.

Note the Importance Of Pre-Natal Exposure TO Hormones.

  • For both 5-alphaRD and AIS we have XY males who do not get the full androgen exposure. But in...

    • 5-alphaRD - result is a male identity

    • • 5-RD prevents external genitalia from developing BUT the brain is still masculinized

    • AIS - result is a female identity

    • the ENTIRE body, including the BRAIN doesn’t respond to androgens and doesn’t have the opportunity to be masculinised

  • CAH in women and tendency toward mroe masculine traits.

  • Thus, it may be the impact of the pre-natal hromones that play a role in organising the brain toward certain gener and sexual preferences.