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PY6020 > Hypothalamic Pituitary Hormones II > Flashcards

Hypothalamic Pituitary Hormones II Flashcards

1
Q

What does the HPG (hypothalamic pituitary gonadal) axis regulate?

A

It regulates reproduction & fertility via increase/decrease in gonadal sex steroids.

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2
Q

How are gonadotropins (e.g. LH/FSH) released?

A

Hypothalamus produces GnRH which binds to receptors of gonadotrophs in the anterior pituitary glands. This then releases gonadotropins.

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3
Q

What type of cells produce testosterone, and further into estrogen?

A

Testicular Leydig cells.

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4
Q

What do testicular sertoli cells do?

A

They respond to FSH to alter gene transcription of sertoli cells and produce enzymes/proteins

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5
Q

What can binding of LH on Leydig cells cause?

A

It can increase the gene transcription of testosterone.

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6
Q

What can the binding of FSH on sertoli cells cause?

A

It can stimulate the transcription of growth hormones, inhibin, and ABP

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7
Q

Why are the activities of LH & FSH different?

A

Because they both have the same alpha chains, but different beta chains which can differentiate their activities.

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8
Q

What is the process of testosterone formation via Leydig cells?

A
  1. LH secreted from pituitary & activates adenylyl cyclase
  2. cAMP & PKA are activated
  3. PKA enters the nucleus & alters gene transcription of enzymes
  4. This converts cholesterol –> testosterone
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9
Q

What is the process of estradiol formation from sertoli cells?

A
  1. Testosterone exiting Leydig cells act on sertoli cells
  2. Sertoli cells convert some of this testosterone into estradiol via aromatase
  3. Some testosterone also leaves into the lumen
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10
Q

What 4 things can be produced when FSH binds to sertoli cells?

A
  1. Androgen inhibiting protein (ABP) - maintains testosterone levels
  2. Aromatase enzyme - converts testosterone to estradiol
  3. Growth factors - supports sperm formation
  4. Inhibins - inhibit FSH secretion
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11
Q

What is the process of the growth hormone axis release?

A

Hypothalamus releases GHRF –> binds to pituitary & produces cAMP as a secondary messenger –>this stimulates somatotrophs –> growth hormone (GH) is then released

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12
Q

How can GHRF release be inhibited?

A

By somatostatin induced decrease in cAMP

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13
Q

What causes dwarfism, and gigantism?

A

Dwarfism: GH deficiency

  • Somatotrophs release less GH than normal
  • Treated with somatorelin analogues

Gigantism: GH excess

  • Bones/hands/feet/face overgrow
  • Somatostatin used as treatment to inhibit excess GH
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14
Q

Which cells secrete prolactin, and what does prolactin assist in?

A

Lactotrophs.

Prolactin assists in breast tissue development, and stimulates lactation in pregnancy

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15
Q

What are the 3 prolactin releasing factors which stimulate prolactin release from lactotrophs?

A
  1. VIP
  2. TRH
  3. PHM
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16
Q

What happens in hyperprolactinemia?

A

Prolactin hypersecretion, which can also decrease sexual function.

In females it can cause:

  • Lack of menstruation
  • Excess milk production

In males:

  • Breast enlargement
  • Decreased libido/sperm
17
Q

What can dopamine agonists and antagonists do in terms of prolactin treatment?

A

DA agonist: increase prolactin

DA antagonist: decrease lactation, and used to treat tumours of lactotrophs

18
Q

What occurs in the posterior lobe of the pituitary gland?

A

Oxytocin & ADH production (from depolarisation/Ca2+ influx)

19
Q

What is anti-diuretic hormone (ADH) also known as?

A

Vasopressin.

20
Q

What does ADH do?

A
  1. Contracts smooth muscles = vasoconstriction

2. Enhances water reabsorption by kidneys/decreasing urine output

21
Q

What factors can affect ADH secretion?

A
  1. Hypotension

2. Increased plasma osmolarity (being more dilute)

22
Q

How many receptors are stimulated by ADH/vasopressin and what do they induce?

A

3 receptors.
V1 - effecting smooth muscle
V2 - anti-diuretic effect on kidneys
V3 - controls ACTH secretion

23
Q

How does ADH produce an anti-diuretic effect on the kidneys?

A
  1. ADH stimulates aquaporin 2 proteins (AQP), also known as water channels
  2. This increases cAMP & PKA
  3. PKA can either: increase aquaporin proteins to cells, or promote gene transcription of new aquaporin proteins
  4. This then promotes the re-uptake of water from the collecting duct
  5. Water is then removed from the urine
24
Q

What is the function of oxytocin in the body?

A

Mediates uterine contractions during birth, and milk ejection.

25
Q

What can stimulate the release of oxytocin from the posterior pituitary gland?

A
  1. Elevated estrogen
  2. Sensory stimuli of cervix/uterus during birth
  3. Suckling of breast during breastfeeding
26
Q

What is the route of administration of oxytocin?

A

IV or nasally, because it is destroyed in the GI if taken orally

27
Q

Why would oxytocin be given to a woman?

A
  1. To induce further oxytocin release
  2. Facilitate pregnancy progression
  3. Lactation assisting
  4. Controlling post-partum uterine haemorrhage

PY6020 (22 decks)

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