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SEM3: PATH30210 Endocrine Health/Disease > L7 Endocrine Physiology of the Testes > Flashcards

L7 Endocrine Physiology of the Testes Flashcards

1
Q

Endocrine Hromones of the Testes?

A

Testosterone (androgen)

  • spermatogenesis
  • sexual maturation (puberty)
  • sexual differentiation (masculinization of reproductive tract
    and external genitalia)

Inhibin: -ve feedback regulation of FSH (gonadotropin)

Anti-müllerian hormone (AMA): sexual differentiation

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2
Q

________ produce a number of hormones including AMH (anti mullerian hormone) and Inhibin. They are the Target for FSH

A

Sertoli Cells produce a number of hormones including AMH (anti mullerian hormone) and Inhibin. They are the Target for FSH

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3
Q
A
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4
Q

__________ released by neuroendocrine cells in arcuate nucleus of the hypothalamus stimulates LH and FSH secretion by gonadotroph cells of the ____________________.

  • LH acts on _________
  • FSH acts on ________

Importance/Regulation?

A

GnRH released by neuroendocrine cells in arcuate nucleus of the hypothalamus stimulates LH and FSH secretion by gonadotroph cells of the anterior pituitary.

  • LH acts on Leydig cells (Testosterone Production)
  • FSH acts on Sertoli cells (Inhibin/AMH Production)

Both are necessary for normal fertility and reproduction!!

Regulation

  • negative feedback by testosterone /inhibin
  • stress
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5
Q

Master hormone controlling fertility and reproduction?

What is Essential for it’s Function?

A

GnRH

Produced in a pulsatile manner by neuroendocrine cells found in the pre-optic region and arcuate nucleus of the hypothalamus (ESSENTIAL FOR NORMAL LH/FSH SECRETION)

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6
Q

Key Ensymes involved in Sex Steroid Synthesis?

A

5-10% testosterone converted to more potent androgen dihydrotestosterone by 5- Alpha reductase

Aromatase converts androgens to estradiol

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7
Q

Testosterone vs. Dihydrotestosterone (DHT)

A

Testosterone and DHT have overlapping but distinct
functions

  • DHT formed from testosterone by 5-alpha reductase
  • DHT is a more potent androgen

In sexual differentiation:

  • Testosterone responsible for the development of internal reproductive tissues (epididymis, seminal vesicles and vas deferens)
  • DHT responsible for the development of male external genitalia and prostate
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8
Q

Pathogenesis of Male Pattern Baldness?

A

In adult males, 5- alpha reductase is highly expressed in prostate and hair follicles (Converts Testoreone => DHT):

  • male pattern baldness=> inhibiting restores hair
  • benign prostatic hyperplasia (BPH)
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9
Q

Hormonal mediation of phenotypic sex?

A

MIS/AMH => regression of Mullerian Duct

Testoerone=> Wolfian Duct transformation to Epididymis, Vas Deferens, Seminal Vessicles, Ejaculatory Duct

Dihydrotestosterone => development of Penis, Scrotum, Prostate

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10
Q

Manifestation of Andropause (Androgen Deficiency Aging Male -ADAM)

A
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11
Q

Incidence/Causes of Male Infertility

A
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12
Q

Cause/Manifestation of Primary Hypogonadism ‘Hypergondadotropic hypogonadism’

A

Gonads not producing enough testosterone despite increases in FSH and LH

Impaired gonadotrophin responsiveness:

  • FSH and LH receptor mutations

Defective androgen synthesis
* 5a-reductase deficiency

LOW Testosterone w/ HIGH levels of gonadotropins

  • LOW testosterone/ DHT
  • HIGH LH/FSH
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13
Q

Cause/Manifestations of 5-Alpha Reductase Deficiency?

A

Autosomal recessive disorder affecting males (DHT absence) leading to phenotypic heterogeneity

Characteristics

  • male gonads have high-frequency cryptorchidism (fail to descend)
  • microphallus, ambiguous or female genitalia (macroclitoris, pseudovagina)
  • amenorrhea and virilisation at puberty in girls
  • males may be fertile/subfertile/infertile often with oligospermia (Low Sperm) or azoospermia (No Sperm)
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14
Q

Cause/Manifestations of Secondary Hypogonadism
‘Hypogonadotropic Hypogonadism’

A

Reduction in both testosterone and gonadotropin (FSH/LH) levels

GnRH insufficiency

Hypopituitarism (tumours, surgical trauma, andropause)

Isolated LH or FSH deficiency

Hyperprolactinemia

Congenital adrenal hyperplasia

Cushings syndrome

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15
Q

Cause/Manifestations of Kallman Syndrome?

A

Inherited disorder of deficient GnRH production

  • Mutations in KAL1 gene interfere with migration of GnRH secreting neurons to hypothalamus during development
  • Characterised by hypogonadotrophic hypogonadism (HH), infertility and absent/incomplete/partial pubertal maturation (LOW FSH, LOW LH, Delayed/absenct puberty)
  • 50% of cases have anosmia or hyposmia (lack of/reduced sense of smell) – distinguishes Kallman syndrome from other HH syndromes
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16
Q

Hypogonadotropic Hypogonadism associated with anosmia or hyposmia (lack of/reduced sense of smell)?

A

Kallman Syndrome

  • Inherited disorder of deficient GnRH production
  • Mutations in KAL1 gene interfere with migration of GnRH secreting neurons to hypothalamus during development
17
Q

Causes/Manifestation of Hyperprolactinemia?

A

Causes

  • 40% of all cases due to benign (functioning) pituitary adenomas (prolactinomas)
  • Other pituitary tumours or pathologies that lower dopamine levels in the hypophyseal portal system (Decrease in Dopamine (Inhibitor) => Hyperprolactienetma)

Manifestations

  • Hyperprolactinemia stimulates lactation (milk production) and interferes with gonadal function (hypogonadism) by suppressing LH and FSH secretion
  • Males: infertility and loss of libido is most common
  • Females: Galactorrhea (Nipple Discharge), Amenorrhea
18
Q

Cause/Manifestations of Insensitivity Syndrome?

A

X linked recessive inheritance => inactivating mutations in androgen receptor

Appear female, have testes, no uterus, no ovaries, external genitalia of female

19
Q

Cause/Manifestation of Cushing’s Disease?

A

Secondary Hypercortisolism due to either pituitary or extrapituitary ACTH excess

Cause:

  • Adrenocorticotropic Hormone (ACTH) stimulates cortisol production AND adrenal androgen production (DHEA)
  • Increased negative feedback regulation by adrenal androgens in hypothalamus and pituitary reduces LH and FSH production

Manifestation

  • Amenorrhea in females
  • Sub/infertility in males
20
Q

Production/Role/Regulation of Adrenal Androgens?

A

Adrenal cortex produces primarily androgens (male sex hormones)

DHEA is the most abundant circulating androgen

  • DHEA weak androgen but can be converted to much more potent testosterone
  • DHEA plays role in the development of secondary sexual characteristics in males and females
  • Adrenal androgen production regulated by ACTH (not pituitary gonadotrophins (LH/FSH)!!)
21
Q

Manifestations of Congenital Adrenal Hyperplasia?

A

Disorders of sexual development due to adrenal androgen (DHEA) and/or estrogen secretion

Males

  • precocious puberty in men (accelerated secondary sexual development)
  • high incidence of infertility

Masculinisation (virilisation) in Women

  • ambiguous genitalia
  • excessive facial hair, virilization
  • menstrual irregularity in adolescence
  • anovulation in adulthood

Rapid early childhood growth but premature closure of epiphyseal growth plate and reduced adult stature

SEM3: PATH30210 Endocrine Health/Disease (25 decks)

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