Reproductive Physiology: Variant Sexual Differentiation
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Questions and Answers

A person has a genetic condition resulting from nondisjunction of sex chromosomes during gametogenesis. What is the most likely cause of this condition?

  • The presence of a dominant gene on an autosome overriding sex chromosome influence.
  • Hormonal imbalances during puberty affecting the development of secondary sexual characteristics.
  • Errors during meiosis causing an abnormal number of sex chromosomes. (correct)
  • A mutation in the SRY gene leading to disrupted gonadal differentiation.

If a person is born with XY chromosomes, but develops phenotypically as female, which of the following is the MOST likely genetic cause?

  • Increased androgen production leading to feminization.
  • A deletion in the X chromosome affecting ovarian development.
  • Overexpression of genes typically found on the X chromosome.
  • Mutation in the SRY gene, preventing normal testis development. (correct)

Which is the correct order of sexual differentiation?

  • Phenotypic, genetic, gonadal
  • Gonadal, genetic, phenotypic
  • Genetic, phenotypic, gonadal
  • Genetic, gonadal, phenotypic (correct)

Which outcome would you expect from a mutation causing complete loss of function of the SRY gene?

<p>Development of female phenotype regardless of chromosomal sex. (D)</p> Signup and view all the answers

A researcher is studying the impact of a new drug on reproductive senescence in males. Which hormonal change would indicate that the drug is successfully delaying andropause?

<p>Increased levels of testosterone (B)</p> Signup and view all the answers

A patient presents with 46,XX DSD due to a deficiency that impairs estrogen production. Which enzyme is most likely deficient?

<p>Aromatase (C)</p> Signup and view all the answers

A newborn with ambiguous genitalia is diagnosed with 46,XY DSD. Genetic testing reveals a mutation affecting the androgen receptor. Which of the following best describes the underlying mechanism?

<p>Inability of cells to respond to androgens, despite their normal production. (D)</p> Signup and view all the answers

Defects in which of the following processes can lead to 46,XY DSD?

<p>All of the above (D)</p> Signup and view all the answers

Which condition associated with 46,XX DSD results in the impaired synthesis of cortisol and androgens?

<p>Congenital adrenal hyperplasia associated with blockade of pregnenolone formation (A)</p> Signup and view all the answers

Which of the following statements accurately describes the role of the hypothalamus in the reproductive axis?

<p>It releases GnRH, which stimulates the release of FSH and LH from the pituitary gland. (C)</p> Signup and view all the answers

A patient is diagnosed with Klinefelter syndrome. Which chromosomal abnormality is the most likely cause?

<p>Seminiferous tubule dysgenesis (A)</p> Signup and view all the answers

Which of the following conditions is characterized by ovarian agenesis?

<p>Turner syndrome (C)</p> Signup and view all the answers

A genetic analysis of a patient reveals a 47,XXX karyotype. Which of the following conditions does this karyotype indicate?

<p>XXX syndrome (D)</p> Signup and view all the answers

What chromosomal abnormality underlies XYY syndrome?

<p>An extra Y chromosome in males (A)</p> Signup and view all the answers

Which of the following best describes ovo-testicular disorder of sex development (OT-DSD)?

<p>A condition in which an individual has both ovarian and testicular tissue (B)</p> Signup and view all the answers

In 46,XY DSD, loss-of-function mutations can lead to which of the following?

<p>Defective testicular development or androgen resistance (A)</p> Signup and view all the answers

What is the primary impact of mutations in the androgen receptor gene?

<p>Androgen resistance (C)</p> Signup and view all the answers

5α-reductase deficiency directly affects the production of which hormone?

<p>Dihydrotestosterone (DHT) (D)</p> Signup and view all the answers

Which of the following conditions is NOT directly caused by a chromosomal abnormality involving the sex chromosomes?

<p>5α-reductase deficiency (C)</p> Signup and view all the answers

Which of the following conditions is NOT typically associated with 46,XX DSD?

<p>Defective testicular development (B)</p> Signup and view all the answers

How do loss-of-function mutations typically impact biological processes?

<p>They reduce or eliminate the function of a gene product. (B)</p> Signup and view all the answers

A newborn female presents with ambiguous genitalia. Genetic testing reveals a 46,XX karyotype. Which of the following is the LEAST likely underlying cause?

<p>5α-reductase deficiency (A)</p> Signup and view all the answers

Which of the following is a characteristic feature of 46,XY DSD related to androgen action?

<p>Inability of cells to respond to androgens (C)</p> Signup and view all the answers

What is the direct consequence of mutations in the androgen receptor gene in individuals with a 46,XY karyotype?

<p>Inability of cells to respond to androgens (B)</p> Signup and view all the answers

Which of the following enzyme deficiencies would directly impair testosterone synthesis in a 46,XY individual?

<p>17α-hydroxylase (B)</p> Signup and view all the answers

A 46,XY individual is diagnosed with 5α-reductase deficiency. Which of the following hormonal profiles is most likely?

<p>Low DHT, normal to high testosterone (C)</p> Signup and view all the answers

Which of the following conditions associated with 46,XX DSD involves the impaired conversion of androgens to estrogens?

<p>Aromatase deficiency (A)</p> Signup and view all the answers

Why might exposure to exogenous androgens during fetal development in a 46,XX fetus lead to virilization?

<p>Exogenous androgens bypass the normal hormonal regulation in the fetus. (A)</p> Signup and view all the answers

A patient presents with elevated levels of FSH and LH, but low levels of estrogen. This hormonal profile is most consistent with which condition?

<p>Turner syndrome (A)</p> Signup and view all the answers

Secondary amenorrhea is characterized by the cessation of menstruation in women who previously had regular cycles. Which of the following is the LEAST likely cause of secondary amenorrhea?

<p>Turner syndrome (D)</p> Signup and view all the answers

Which of the following conditions is characterized by a resistance to Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)?

<p>FSH or LH resistance (D)</p> Signup and view all the answers

A female patient is diagnosed with primary amenorrhea. Further testing reveals anosmia (loss of smell). Which of the following conditions is most likely responsible for these findings?

<p>Kallmann syndrome (B)</p> Signup and view all the answers

Which of the following best describes the mechanism by which stress can lead to hypothalamic amenorrhea?

<p>Decreased hypothalamic dopamine secretion, leading to increased prolactin secretion and decreased GnRH release (C)</p> Signup and view all the answers

A 48-year-old female reports irregular menstrual cycles, hot flashes, and difficulty sleeping. These symptoms are most likely related to a decline in the number of:

<p>Ovarian follicles (C)</p> Signup and view all the answers

Which of the following is a key difference between primary and secondary amenorrhea?

<p>Primary amenorrhea is the absence of menstruation by age 16, while secondary amenorrhea is the cessation of menstruation after previous cycles. (B)</p> Signup and view all the answers

Which of the following conditions directly impairs the release of GnRH?

<p>Kallmann syndrome (D)</p> Signup and view all the answers

How does a prolactin-secreting pituitary adenoma disrupt the reproductive axis?

<p>By suppressing GnRH release. (D)</p> Signup and view all the answers

A patient with anorexia nervosa is likely to develop amenorrhea due to which mechanism?

<p>Decreased GnRH release due to low body fat and metabolic stress (D)</p> Signup and view all the answers

Flashcards

Sexual Differentiation

The process by which individuals develop male or female characteristics.

Levels of Sexual Differentiation

Genetic, Gonadal, Phenotypic (anatomic)

Genetic Sex (Male)

XY pattern.

Genetic Sex (Female)

XX pattern.

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Genetic Errors in Sexual Differentiation

Errors during meiosis (gamete formation) that can lead to atypical sex chromosome numbers.

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46,XX DSD

A condition with a mismatch between chromosomal sex (XX) and phenotypic sex.

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46,XY DSD

Results from conditions affecting testicular formation or androgen action.

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Congenital Adrenal Hyperplasia (related to pregnenolone)

Blocks pregnenolone, affecting steroid hormone synthesis.

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Congenital 17α-hydroxylase deficiency

An enzyme deficiency impacting both androgen and estrogen production.

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GnRH neurons

Neurons in the hypothalamus that release GnRH, regulating FSH and LH.

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DSD

Disorders of Sex Development.

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Exogenous androgens

Excessive androgen exposure during development.

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Defective testicular development

When the testicles do not develop correctly.

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Androgen resistance

Body's cells don't respond to androgens.

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5α-reductase deficiency

The body cannot convert testosterone to dihydrotestosterone (DHT).

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Loss of function mutations

Genetic changes that cause loss of any function.

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Klinefelter Syndrome

A genetic condition in males resulting from an extra X chromosome (47, XXY), leading to seminiferous tubule dysgenesis.

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Turner Syndrome

A genetic disorder in females due to a missing or structurally altered X chromosome (45, X), resulting in ovarian agenesis.

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XXX Syndrome

A chromosomal condition in females where there are three X chromosomes (47, XXX).

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XYY Syndrome

A chromosomal condition in males where there is an extra Y chromosome (47, XYY).

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Ovo-testicular DSD

A disorder of sex development where an individual has both ovarian and testicular tissue.

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Variant Sexual Differentiation

Conditions where the typical development of sex chromosomes, gonads, or anatomy is altered.

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Mutations in Androgen Receptor Gene

A genetic condition caused by mutations affecting the gene for the androgen receptor.

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FSH and LH

Hormones secreted by pituitary gland that regulate gonadal function.

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Inhibin, Estrogen, Progesterone

Hormones secreted by the gonads that have feedback effects on the hypothalamus and pituitary.

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Hypergonadotropic Hypogonadism

A condition resulting from gonadal failure and elevated gonadotropin levels.

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Hypogonadotropic Hypogonadism

A condition resulting from impaired hypothalamic or pituitary function, leading to low gonadotropin levels

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Amenorrhea

Absence of menstruation

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Primary Amenorrhea

Menstruation never started by age 16.

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Secondary Amenorrhea

Cessation of menstruation after it has previously occurred.

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Menopause

Caused by gradual decline in the number of ovarian follicles.

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Andropause

Period of declining reproductive function in males.

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Study Notes

  • Variant Male & Female Reproductive Physiology is explored

Variant Sexual Differentiation

  • Explores Chromosomal Abnormalities
  • Explores Genetic Mutations

Dysregulation of the Reproductive Axis

  • Addresses Primary & Secondary Gonadal Insufficiencies

Reproductive Senescence

  • Covers Menopause
  • Covers Andropause

Sexual Differentiation

  • Sexual differentiation operates on three levels: genetic, gonadal, and phenotypic

Genetic Level

  • Male genetic pattern is XY
  • Female genetic pattern is XX

Gonadal Level

  • The Y chromosome determines differentiation
  • This determination stems from the SRY gene, which acts as the testis-determining factor

Phenotypic Level

  • This level is anatomic

Variant Sexual Differentiation

  • Genetic errors may arise from non-disjunction of sex chromosomes during gametogenesis (meiosis)

Impact of Errors in Gametogenesis

  • Seminiferous tubule dysgenesis, known as Klinefelter syndrome, can occur
  • Ovarian agenesis, known as Turner syndrome, can occur
  • 47, XXX (XXX syndrome) can occur
  • 47, XYY (XYY syndrome) can occur
  • Ovo-testicular disorder of sex development (OT-DSD) can occur
  • Includes other chromosomal abnormalities beyond those listed

Loss of Function Mutations & Disorders of Sex Development (DSD)

  • 46, XY DSD, includes defective testicular development as well as androgen resistance
  • Androgen resistance can further stem from 5α-reductase deficiency or mutations in the androgen receptor gene
  • Can be congenital adrenal hyperplasia associated with blockade of pregnenolone formation
  • Can be congenital 17α-hydroxylase deficiency
  • 46, XX DSD, includes congenital adrenal hyperplasia, aromatase deficiency, and exposure to exogenous androgens

Neural & Endocrine Regulation of the Reproductive Axis

Hypothalamus

  • Gonadotropin-releasing hormone (GnRH) neurons stimulate FSH & LH release
  • GnRH regulated directly & indirectly by hormonal & neural inputs

Pituitary

  • Releases FSH and LH

Gonads

  • Release inhibin, estrogen, and progesterone

Neural & Endocrine Control of the Reproductive Axis

  • Disruption of reproductive axis leads to hypergonadotropic hypogonadism and hypogonadotropic hypogonadism

Disruption of the Reproductive Axis

  • Amenorrhea occurs

Primary Amenorrhea

  • An example is anorexia nervosa

Secondary Amenorrhea

  • Examples include pregnancy and lactation and decreased body fat

Hypergonadotropic Hypogonadism

  • Can be caused by Turner syndrome (ovarian agenesis)
  • Can be caused by FSH or LH resistance
  • Can be caused by aromatase deficiency
  • Can be caused by menopause

Hypogonadotropic Hypogonadism

  • Can be caused by Kallmann syndrome
  • Can be caused by GnRH resistance
  • Can be caused by Prader-Willi syndrome
  • Can be caused by anorexia nervosa
  • Can be caused by hypothalamic amenorrhea

Other Causes of Hypothalamic Amenorrhea

  • Prolactin-secreting pituitary adenomas decrease GnRH release
  • Stress leads to decreased hypothalamic dopamine secretion, increased prolactin secretion, and decreased GnRH release

Reproductive Senescence

Menopause

  • Menopause is caused by a gradual decline in the number of ovarian follicles

Climacteric

  • Refers to effects on the reproductive tract and other effects

Andropause

Abnormal Male & Female Reproductive Physiology Lecture Review

  • Variant Sexual Differentiation includes chromosomal abnormalities (e.g., Turner syndrome) or genetic mutations (e.g., 21-hydroxylase deficiency)
  • Dysregulation of the Reproductive Axis includes hypergonadotropic hypogonadism (e.g., Menopause) and hypogonadotropic hypogonadism (e.g., Kallmann syndrome)
  • In women, 1° amenorrhea starts before puberty, 2° amenorrhea if it starts after puberty

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Description

Explore variant male and female reproductive physiology, including chromosomal abnormalities and genetic mutations. Understand dysregulation of the reproductive axis, addressing primary and secondary gonadal insufficiencies. Reproductive senescence, menopause, and andropause are also covered.

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