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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
On which type of receptors do sex steroid hormones act?
Nuclear receptors.
26
On which domain of the receptor do sex steroid hormones act?
The steroid response elements.
27
List 3 carrier proteins that bind to sex steroid hormones.
1 - Albumin. 2 - Sex hormone-binding globulin. 3 - Androgen binding protein.
28
Outline the metabolic products of sex steroid hormone production.
1 - Cholesterol is converted into progestogens. 2 - Progestogens are converted into androgens. 3 - Androgens are converted into oestrogens.
29
List 4 progestogens.
1 - Pregnenolone. 2 - 17 alpha-hydroxypregnenolone. 3 - Progesterone. 4 - 17 alpha-hydroxyprogesterone.
30
List 5 androgens.
1 - Dehydroepiandrosterone. 2 - Androstenediol. 3 - Androstenedione. 4 - Testosterone. 5 - Dihydrotestosterone.
31
List 3 oestrogens. In which stages of life are these hormones particularly active?
1 - Oestrone (post-menopause). 2 - Oestradiol (puberty to menopause). 3 - Oestriol (pregnancy).
32
Where in the cells are the enzymes located that are involved in the production of sex steroid hormones? What is the exception?
- In the smooth endoplasmic reticulum. | - The exception is the cholesterol side-chain cleavage enzyme, which is found in the mitochondria.
33
What is the function of cholesterol side-chain cleavage enzyme?
It converts cholesterol into pregnenolone (the first step for sex steroid hormone production).
34
List 5 functions of progestogens.
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
List the receptors for progestogens.
1 - PR-A. 2 - PR-B
36
List 5 functions of androgens.
1 - Development and maintenance of the male reproductive system. 2 - Secondary sexual characteristics. 3 - Sexual function. 4 - Support spermatogenesis. 5 - Regulation of gonadotropins.
37
Which exon of the androgen receptor is polymorphic? What is the advantage of this polymorphism?
- Exon 1. | - The androgen receptor can show differing sensitivities to androgens.
38
List 4 functions of oestrogens.
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
Give an example of a sex steroid hormone that binds to receptors of classes other than their own.
Synthetic progestogens in contraceptive medication can bind to androgen receptors, causing side effects such as acne.
40
Give an example of a sex steroid hormone receptor antagonist.
Mifepristone antagonises progestogens by binding to progestogen receptors (without causing activation).
41
How do sex steroids interact with gonadotropins?
Sex steroids are both regulated by and regulate gonadotropins of the anterior pituitary (FSH and LH) via feedback loops.
42
Which component of the HPG axis is dysfunctional with central hypogonadism?
The hypothalamus and / or pituitary.
43
Which component of the HPG axis is dysfunctional with primary hypogonadism?
The gonads.
44
Which component of the HPG axis is dysfunctional with secondary hypogonadism?
The hypothalamus and / or pituitary.
45
Which sex is more likely to experience endocrine causes of infertility?
Females.
46
When do levels of prolactin increase?
During pregnancy and breastfeeding.
47
What is the function of prolactin?
To inhibit gonadal activity by suppression of gonadotropin-releasing hormone from the hypothalamus. This causes lactational amenorrhoea.
48
Define lactational amenorrhoea.
Temporary postnatal infertility that occurs when a woman is amenorrhoeic and fully breastfeeding.
49
# Define amenorrhoea. What is the difference between primary and secondary amenorrhoea?
- 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
What is a complication of hyperprolactinaemia?
Galactorrhea (the abnormal production of breast milk).
51
How does gametogenesis in males differ from gametogenesis in females?
- In males, gametogenesis is continuous. | - In females, gametogenesis is cyclic (one oocyte is produced per month).
52
What is the average duration of the menstrual cycle?
26-32 days.
53
List the phases of the menstrual cycle.
1 - Menstruation (first day of bleeding). 2 - Follicular phase. 3 - Ovulation. 4 - Luteal phase.
54
How long is the luteal phase of the menstrual cycle?
14 days.
55
Which phase of the menstrual cycle is variable in length?
The follicular phase.
56
By convention, when are FSH and LH measured clinically?
At day 2 or 3 of the menstrual cycle.
57
# Define ovarian reserve. How can ovarian reserve be measured?
- 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
What is the purpose of testing for progesterone? When is progesterone tested for?
- Used as a test for ovulation. | - At 21 days of the menstrual cycle (half way through the luteal phase).
59
Define oligomenorrhoea.
Irregular time between periods, defined as <9 cycles in 12 months.
60
Define menorrhagia.
Heavy periods.
61
Define dysmenorrhea.
Painful periods.
62
List 3 hormonal changes that accompany menopause.
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
Describe the mechanism that underpins hormonal contraception.
Synthetic progestogens and oestrogens suppress ovulation, thicken the cervical mucus and thin the endometrium.
64
How is prostate cancer treated by altering the HPG axis?
Gonadotropin-releasing hormone antagonists suppress T cell production.

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