PSY 345

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PSY 345

• Organizational and Activational Effects of
  Hormones

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The Role of the Endocrine System in Reproductive
Behavior

• All cells of the body contain 23 pairs of
  chromosomes including a pair of sex chromosomes,
  XX or XY.
• Female gametes only contain X sex chromosomes.
• Male gametes contain either X or Y sex
  chromosomes.

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Human Chromosomes
The Sex Chromosomes
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Sexual Differentiation

• Cells in both males and females contain the
  genetic code necessary to produce phenotypic
  males or females.
• What determines the phenotypic (and behavioral)
  sex of the organism is pre-natal exposure to
  androgens.
• The Y chromosome carries the genetic information
  necessary to initiate production of androgens.

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Sexual Differentiation of the Gonads

• In humans the sexes look alike until the ninth
  week of development.
• During the fifth week embryos develop
  undifferentiated gonads Primordial Gonads.
• One set of tubes can develop into female sex
  organs Mullerian Ducts
• The other set can develop into male sex organs
  Wolffian Ducts

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Primordial Gonads
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The Y Chromosome

• The SRY gene on the Y chromosome codes for the
  protein Testes Determining Factor (TDF)
• TDF is a Transcription Factor It causes other
  genes to turn on.
• TDF causes primordial gonads to secrete
  testosterone and T causes gonads to develop into
  testes Promotion of the Wolffian Ducts
• TDF also causes the developing testes to secrete
  anti-Mullerian hormone Inhibition of the
  Mullerian Ducts

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The Effect of No Y Chromosome

• In the absence of a Y chromosome the Wolffian
  Ducts regress on there own.
• Wolffian ducts must have T to develop
• The Mullerian Ducts will continue to develop on
  their own creating ovaries.
• Hence, natures impulse is to create a female

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External Genitalia

• Testosterone is converted to Dihydrotestosterone
  (DHT), a more potent androgen
• DHT causes external skin to grow into penis and
  scrotum
• DHT causes development of prostate.
• No DHT no prostate labia

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Sex Limited Effects

• Males and females of many species show sexual
  dimorphism.
• Height
• Facial Hair
• Waist to Hip ratio
• Voice Pitch
• Sexual dimorphism is produced by exposure to
  hormones.
• Sex hormones switch on certain genes and turn off
  others. These genes are called Sex Limited Genes.

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When things go wrong.

• The following slides depict several disorders of
  the endocrine system specifically those that
  deal with the reproductive system or sex-limited
  genes. If you are squeamish you may want to
  cover your eyes with your hands and peak through
  your fingers.

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Gynocomastia

• Gynecomastia is a medical term that comes from
  the Greek words for "woman - like breasts."
  Though this oddly named condition is rarely
  talked about, it is actually quite common.
  Gynecomastia affects an estimated 40 to 60 of
  men.

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Overview of causes

• use of anabolic steroids
• herbal testosterone additives
• Hypogonadal syndrome
• impaired liver function
• use of estrogen containing medications and other
  medications
• problems of testicular hormone production
• and many others

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Anabolic steroids and other testosterone boosters.

• Whenever the normal ratio of androgens to
  estrogens is changed problems can occur in
  sex-limited effects.
• Remember the body wants to maintain homeostasis.
• Excess testosterone is aromatized to estradiol a
  feminizing hormone. This activates female sex
  limited genes.
• This results in the development of female
  phenotypical characteristics such as enlarged
  breasts.

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Hypogonadism (decreased androgens or increased
resistance to androgen)

• Primary
• Acquired (trauma, infection, torsion (twisted
  testicles), radiation,mumps, chemotherapy)
• Congenital
• Secondary
• Hypogonadotropic Hypogonadism (low testicular
  function from lack of gonadal stimulating
  pituitary hormones
• Kallmann Syndrome An x-linked disorder
  characterized by a GnRH deficiency with
  hypogonadotropic hypogonadism and delayed
  puberty, and smelling deficiencies.
• Pituitary Failure (Loss of blood supply,
  infection, tumor)

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Miscellaneous

• Alcoholism impaired liver function
• Chest Wall Trauma
• Cystic Fibrosis
• Herpes Zoster Infection
• HIV (after years of highly active antiretroviral
  therapy (HAART))
• Myotonic Dystrophy (an inherited disorder in
  which the muscles contract but have decreasing
  power to relax, become weak and waste away)
• Obesity
• Psychological Stress
• Spinal Cord Injury
• Refeeding after Malnutrition (increased materials
  for peripheral tissue aromatase)

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Treatment?
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Congenital Adrenal Hyperplasia an autosomal
recessive disorder

• Recall that sexual differentiation occurs in the
  presence of prenatal androgens.
• Both the brain and sex organs differentiate.
• Congenital adrenal hyperplasia CAH, is a
  condition where there is a metabolic block in the
  synthesis of cortisol in the adrenal glands.
• A block in this metabolic pathway can produce a
  build up of cortisol precursors. 21-hydroxylase
  deficiency.
• Cortisol precursors are also precursors for
  testosterone.

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CAH 21-hydroxylase deficiency

• In XY individuals the abundance of testosterone
  can cause high blood pressure and excessive salt
  loss.
• In XX individuals the internal sex organs develop
  normally
• lack of Mullerian regression hormone.
• The high dose of androgens masculinizes the
  development of the external genitalia
  Virilization
• The extent of virilization is variable
• Clitoral enlargement
• Ambiguous genetalia
• Male typical genetalia

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Congenital adrenal hyperplasia

• CAH typically requires surgical intervention

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Behavioral Effects of CAH Gender Role

• XX individuals with CAH typically receive
  exogenous estrogens.
• However, they still display more male typical
  behaviors than normal females.
• Increased rough and tumble play
• Characterized as tomboys
• Prefer male playmates
• Prefer male typical toys
• Engage in fewer games simulating maternal care
• Less interest in personal appearance
• Fewer fantasies concerning marriage

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Behavioral Effects of CAH Sexual Orientation

• Females with CAH who are surgically corrected and
  reared as females are generally attracted to
  males.
• However, they are 4 times as likely to have
  engaged in at least one same sex encounter by
  adulthood.
• They also show a higher than typical rate of same
  sex fantasy than normal females.
• Possible organizational effects of androgens on
  developing nervous system

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Androgen Insensitivity Syndrome

• Androgen Insensitivity (A.I.) A genetic mutation
  that prevents the formation of androgen
  receptors.
• A.I. Is caused by a point mutation in the gene
  coding for the androgen receptor protein on the X
  chromosome.
• XX females with the defective allele are
  unaffected as they have one functioning gene.
• There are no XX females homozygous for the
  defective allele. Hmmmmn!

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Androgen Insensitivity

• XY (Males) with A.I. develop testes (TDF is
  present from Y chromosome) which produce
  testosterone and Mullerian inhibiting hormone
  (normal).
• Female internal sex organs regress.
• However, because cells cannot respond to
  testosterone, genitalia is female with no
  internal sex organs (male or female).
• Normal testes produce small amounts of estrodiol
  and at puberty this feminizes the individual.

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XY female with Androgen Insensitivity
Syndrome. Note absence of body hair due to
insensitivity to DHT (an androgen).
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Androgen Insensitivity

• XY individuals appear as normal females and
  regard themselves as female.
• They show no psychological differences to normal
  females in regards to gender role and sexual
  preference.
• Why no XX females homozygous for A.I.?
• Get out the Square!

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Map of the Y Chromosome