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RED > Introduction and HPG Axis > Flashcards

Introduction and HPG Axis Flashcards

1
Q

Describe the HPG axis in males.

A

1 - The hypothalamus secretes gonadotropin-releasing hormone (GnRH).

2 - Gonadotropin-releasing hormone stimulates the anterior pituitary to release FSH and LH.

3 - FSH and LH stimulate the testes to produce inhibin and testosterone.

4 - Inhibin has a negative feedback effect on the anterior pituitary.

5 - Testosterone has a negative feedback effect on the anterior pituitary and hypothalamus.

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2
Q

How does the female HPG axis differ from the male HPG axis?

A

1 - Oestrogen and progesterone replace inhibin and testosterone.

2 - Both oestrogen and progesterone have a negative feedback effect on both the anterior pituitary and hypothalamus (whereas inhibin only affects the anterior pituitary).

3 - Oestrogen can also have a positive feedback effect on both the anterior pituitary and hypothalamus.

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3
Q

Briefly describe the position of the hypothalamus.

A

At the base of the brain between the midbrain and forebrain.

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4
Q

What type of molecule is gonadotropin-releasing hormone?

A

A peptide.

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5
Q

How many amino acids are contained in gonadotropin-releasing hormone?

A

10.

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6
Q

What is Kallmann syndrome?

A

Failure of gonadotropin-releasing hormone-secreting neurones to migrate during development, causing infertility.

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7
Q

At puberty, what triggers gonadal activation?

A

Pulsatile gonadotropin-releasing hormone secretion.

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8
Q

Describe the mechanism by which the pituitary acquires resistance to the effects of gonadotropin-releasing hormone.

A

Continuous gonadotropin-releasing hormone secretion leads to downregulation of gonadotropin-releasing hormone receptors on the surface of gonadotroph cells in the pituitary.

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9
Q

List 6 hormones secreted by the anterior pituitary gland.

A

1 - Adrenocorticotropic hormone.

2 - Thyroid-stimulating hormone.

3 - Growth hormone.

4 - Luteinising hormone.

5 - Follicle-stimulating hormone.

6 - Prolactin.

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10
Q

List 2 hormones secreted by the posterior pituitary.

A

1 - Antidiuretic hormone.

2 - Oxytocin.

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11
Q

List the hormones secreted by gonadotrophs.

Give an example of another other gonadotropin that is not secreted by gonadotrophs.

A

1 - Follicle-stimulating hormone.

2 - Luteinising hormone.

3 - Human chorionic gonadotropin.

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12
Q

Give an example of a hormone secreted by corticotrophs.

A

Corticotrophs secrete adrenocorticotropic hormone.

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13
Q

Give an example of a hormone secreted by somatotrophs.

A

Somatotrophs secrete growth hormone.

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14
Q

Give an example of a hormone secreted by lactotrophs.

A

Lactotrophs secrete prolactin.

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15
Q

What type of molecules are FSH and LH?

A

FSH and LH are glycoproteins.

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16
Q

What type of receptors are targeted by FSH and LH?

A

FSH and LH target G protein-coupled receptors.

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17
Q

Which cells secrete chorionic gonadotropin?

A

Trophoblast cells secrete chorionic gonadotropin.

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18
Q

List the targets of LH.

A

1 - Leydig cells (male).

2 - Theca cells (female).

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19
Q

List the targets of FSH.

A

1 - Sertoli cells (male).

2 - Granulosa cells (female).

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20
Q

What is the target of chorionic gonadotropin?

A

Luteal cells of the corpus luteum.

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21
Q

List the receptors for gonadotropins.

State the hormone that binds to each receptor.

A

1 - Luteinizing hormone-choriogonadotropin receptor (LHCGR): LH and chorionic gonadotropin.

2 - Follicle-stimulating hormone receptor (FSHR): FSH.

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22
Q

List the routes of communication from the hypothalamus to the pituitary.

A

1 - Direct neural connection.

2 - Indirect via the vasculature.

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23
Q

List the families of sex steroid hormones.

State the locations in the body from which each family is released.

A

1 - Progestogens (released from the gonads and placenta).

2 - Androgens (released from the gonads and adrenal glands).

3 - Oestrogens (released from the gonads, liver, adrenal glands, adipose tissue and the placenta).

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24
Q

From which molecule are sex steroid hormones derived?

A

Cholesterol.

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25
Q

On which type of receptors do sex steroid hormones act?

A

Nuclear receptors.

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26
Q

On which domain of the receptor do sex steroid hormones act?

A

The steroid response elements.

27
Q

List 3 carrier proteins that bind to sex steroid hormones.

A

1 - Albumin.

2 - Sex hormone-binding globulin.

3 - Androgen binding protein.

28
Q

Outline the metabolic products of sex steroid hormone production.

A

1 - Cholesterol is converted into progestogens.

2 - Progestogens are converted into androgens.

3 - Androgens are converted into oestrogens.

29
Q

List 4 progestogens.

A

1 - Pregnenolone.

2 - 17 alpha-hydroxypregnenolone.

3 - Progesterone.

4 - 17 alpha-hydroxyprogesterone.

30
Q

List 5 androgens.

A

1 - Dehydroepiandrosterone.

2 - Androstenediol.

3 - Androstenedione.

4 - Testosterone.

5 - Dihydrotestosterone.

31
Q

List 3 oestrogens.

In which stages of life are these hormones particularly active?

A

1 - Oestrone (post-menopause).

2 - Oestradiol (puberty to menopause).

3 - Oestriol (pregnancy).

32
Q

Where in the cells are the enzymes located that are involved in the production of sex steroid hormones?

What is the exception?

A
  • In the smooth endoplasmic reticulum.

- The exception is the cholesterol side-chain cleavage enzyme, which is found in the mitochondria.

33
Q

What is the function of cholesterol side-chain cleavage enzyme?

A

It converts cholesterol into pregnenolone (the first step for sex steroid hormone production).

34
Q

List 5 functions of progestogens.

A

1 - Preparation of uterus for pregnancy.

2 - Maintenance of uterus during pregnancy.

3 - Growth of mammary glands.

4 - Suppression of lactation.

5 - Catabolic effects.

6 - Regulation of gonadotropins.

35
Q

List the receptors for progestogens.

A

1 - PR-A.

2 - PR-B

36
Q

List 5 functions of androgens.

A

1 - Development and maintenance of the male reproductive system.

2 - Secondary sexual characteristics.

3 - Sexual function.

4 - Support spermatogenesis.

5 - Regulation of gonadotropins.

37
Q

Which exon of the androgen receptor is polymorphic?

What is the advantage of this polymorphism?

A
  • Exon 1.

- The androgen receptor can show differing sensitivities to androgens.

38
Q

List 4 functions of oestrogens.

A

1 - Secondary sexual characteristics.

2 - Stimulation of growth and activity of mammary glands.

3 - Stimulation and proliferation of the endometrium for progesterone action.

4 - Regulation of gonadotropins.

39
Q

Give an example of a sex steroid hormone that binds to receptors of classes other than their own.

A

Synthetic progestogens in contraceptive medication can bind to androgen receptors, causing side effects such as acne.

40
Q

Give an example of a sex steroid hormone receptor antagonist.

A

Mifepristone antagonises progestogens by binding to progestogen receptors (without causing activation).

41
Q

How do sex steroids interact with gonadotropins?

A

Sex steroids are both regulated by and regulate gonadotropins of the anterior pituitary (FSH and LH) via feedback loops.

42
Q

Which component of the HPG axis is dysfunctional with central hypogonadism?

A

The hypothalamus and / or pituitary.

43
Q

Which component of the HPG axis is dysfunctional with primary hypogonadism?

A

The gonads.

44
Q

Which component of the HPG axis is dysfunctional with secondary hypogonadism?

A

The hypothalamus and / or pituitary.

45
Q

Which sex is more likely to experience endocrine causes of infertility?

A

Females.

46
Q

When do levels of prolactin increase?

A

During pregnancy and breastfeeding.

47
Q

What is the function of prolactin?

A

To inhibit gonadal activity by suppression of gonadotropin-releasing hormone from the hypothalamus. This causes lactational amenorrhoea.

48
Q

Define lactational amenorrhoea.

A

Temporary postnatal infertility that occurs when a woman is amenorrhoeic and fully breastfeeding.

49
Q

Define amenorrhoea.

What is the difference between primary and secondary amenorrhoea?

A
  • The absence of menstruation between puberty and menopause for 6 months.
  • Primary amenorrhoea is amenorrhoea in women that have never menstruated.
  • Secondary amenorrhoea is amenorrhoea in women that have previously menstruated.
50
Q

What is a complication of hyperprolactinaemia?

A

Galactorrhea (the abnormal production of breast milk).

51
Q

How does gametogenesis in males differ from gametogenesis in females?

A
  • In males, gametogenesis is continuous.

- In females, gametogenesis is cyclic (one oocyte is produced per month).

52
Q

What is the average duration of the menstrual cycle?

A

26-32 days.

53
Q

List the phases of the menstrual cycle.

A

1 - Menstruation (first day of bleeding).

2 - Follicular phase.

3 - Ovulation.

4 - Luteal phase.

54
Q

How long is the luteal phase of the menstrual cycle?

A

14 days.

55
Q

Which phase of the menstrual cycle is variable in length?

A

The follicular phase.

56
Q

By convention, when are FSH and LH measured clinically?

A

At day 2 or 3 of the menstrual cycle.

57
Q

Define ovarian reserve.

How can ovarian reserve be measured?

A
  • How many eggs remain in a woman’s ovaries.

- Can be measured by measuring FSH and LH levels at day 2 or 3 of the menstrual cycle and comparing the normal values.

58
Q

What is the purpose of testing for progesterone?

When is progesterone tested for?

A
  • Used as a test for ovulation.

- At 21 days of the menstrual cycle (half way through the luteal phase).

59
Q

Define oligomenorrhoea.

A

Irregular time between periods, defined as <9 cycles in 12 months.

60
Q

Define menorrhagia.

A

Heavy periods.

61
Q

Define dysmenorrhea.

A

Painful periods.

62
Q

List 3 hormonal changes that accompany menopause.

A

1 - Production of progesterone ceases.

2 - Production of oestrogen ceases.

3 - Loss of negative feedback by sex steroids leads to high FSH and LH levels.

63
Q

Describe the mechanism that underpins hormonal contraception.

A

Synthetic progestogens and oestrogens suppress ovulation, thicken the cervical mucus and thin the endometrium.

64
Q

How is prostate cancer treated by altering the HPG axis?

A

Gonadotropin-releasing hormone antagonists suppress T cell production.

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