Reproduction/ Sex Steroid Axis

Question 1

What hormone does the hypothalamus release to start the reproductive axis?

Answer 1

gonadotropin-releasing hormone (GnRH)

Question 2

How is GnRH secreted from the hypothalamus?

Answer 2

GnRH is secreted pulsatile, which is important for normal function

Question 3

What hormones are released by the anterior pituitary in response to GnRH?

Answer 3

1. Luteinizing hormone (LH)
2. Follicle-stimulating hormone (FSH).

Question 4

What is the role of luteinizing hormone (LH) in females?

Answer 4

= LH triggers ovulation in females
= stimulates the production of oestrogen from the ovaries

Question 5

What is the role of follicle-stimulating hormone (FSH) in females?

Answer 5

FSH stimulates follicle maturation in the ovaries and promotes the production of oestrogen

Question 6

What is the role of luteinizing hormone (LH) in males?

Answer 6

LH stimulates the production of testosterone from the testes

Question 7

What is the role of follicle-stimulating hormone (FSH) in males?

Answer 7

FSH stimulates sperm production in the testes

Question 8

What hormones are produced by the ovaries in response to LH and FSH in females?

Answer 8

1. Oestrogens (e.g., estradiol)
2. Progesterone in response to LH and FSH

Question 9

What are the functions of oestrogen in females?

Answer 9

Oestrogen is responsible for the development of female secondary sexual characteristics (eg, breasts) and regulates the menstrual cycle

Question 10

What is the function of progesterone in females?

Answer 10

Progesterone prepares the uterus for implantation and maintains pregnancy

Question 11

What hormones are produced by the testes in males in response to LH and FSH?

Answer 11

testosterone and inhibin

Question 12

What are the functions of testosterone in males?

Answer 12

Testosterone regulates male secondary sexual characteristics
(eg, facial hair, deep voice), sperm production, and libido

Question 13

What is the role of inhibin in males?

Answer 13

Inhibin inhibits FSH production to regulate sperm production

Question 14

What type of feedback mechanism is primarily used to regulate the sex steroid axis?

Answer 14

The sex steroid axis is primarily regulated by negative feedback

Question 15

How do high levels of sex steroids
(eg, oestrogen, testosterone) affect the hypothalamus and pituitary?

Answer 15

High levels of sex steroids inhibit the release of GnRH, LH, and FSH from the hypothalamus and pituitary

Question 16

What is the positive feedback mechanism in the reproductive axis?

Answer 16

Positive feedback occurs during the ovulatory cycle in females, when high levels of oestrogen increase GnRH secretion, leading to a surge in LH, which triggers ovulation

Question 17

What are the phases of the menstrual cycle in females?

Answer 17

The menstrual cycle has the following phases

(1) Follicular phase
= FSH stimulates follicle development and oestrogen increases

(2) Ovulation
= LH and FSH surge due to high oestrogen

(3) Luteal phase
= Post-ovulation, the corpus luteum secretes progesterone

(4) Menstruation
= If pregnancy doesn’t occur, progesterone drops, leading to the shedding of the uterine lining

Question 18

How do sex steroids contribute to sexual development?

Answer 18

In females, oestrogen regulates the development of breasts, wider hips, and other female secondary sexual characteristics

In males, testosterone regulates the development of a deeper voice, facial and body hair, and muscle growth

Question 19

What are LH and FSH, and where are they produced?

Answer 19

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are glycoproteins produced and secreted by the anterior pituitary gland

Question 20

What stimulates the release of LH and FSH?

Answer 20

Gonadotropin-releasing hormone (GnRH)

Question 21

How do sex steroids affect the secretion of LH and FSH?

Answer 21

Sex steroids exert a negative feedback effect on the secretion of LH and FSH

Question 22

How do LH and FSH levels vary during the menstrual cycle in females?

Answer 22

LH and FSH levels rise in the follicular phase, peak around ovulation, and then fall.

LH reaches higher plasma concentrations than FSH at ovulation

Question 23

What is the function of FSH in males and females?

Answer 23

(1) In males, FSH acts on Sertoli cells to support spermatogenesis

(2) In females, it stimulates follicular development and oestrogen production

Question 24

What is the function of LH in males and females?

Answer 24

(1) In males, LH acts on Leydig cells to produce testosterone

(2) In females, LH helps in corpus luteum development and progesterone production

Question 25

What is hypergonadotropic hypogonadism, and which conditions are associated with it?

Answer 25

Characterised by higher-than-normal levels of FSH and LH. It is associated with conditions such as 1. ovarian failure = postmenopausal, premature ovarian failure 2. Klinefelter syndrome

Question 26

What is hypogonadotropic hypogonadism, and what causes it?

Answer 26

Characterised by lower-than-normal levels of FSH and LH. It can be caused by conditions like 1. hypopituitarism 2. prolactinoma 3. anabolic steroid use 4. Kallmann’s syndrome

Question 27

FSH and LH are secreted by which structure?

Answer 27

The anterior pituitary gland

Question 28

What does the mid-cycle LH surge trigger?

Answer 28

Ovulation

Question 29

What is the hormone produced as a result of the stimulation of follicle-stimulating hormone (FSH) on its target tissue?

Answer 29

Oestradiol

Question 30

What are the target organ and target cells of the follicle-stimulating hormone (FSH)?

Answer 30

Ovary - granulosa cells

Question 31

What is the hormone produced as a result of stimulation by luteinising hormone (LH) on its target tissue?

Answer 31

Progesterone/testosterone

Question 31

What is the mechanism of action of Domperidone?

Answer 31

Dopamine D2 receptor antagonist

Question 32

Urinary pregnancy tests identify the presence of which molecule?

Answer 32

beta-HCG

Question 33

What are the target organ and target cells of the luteinising hormone (LH)?

Answer 33

Ovary - theca cells

Question 34

What is the term used to describe hormones which act on their target tissues to induce secretion of another hormone?

Answer 34

Tropic hormones

Question 35

Which enzyme is deficient in 95% of Congenital Adrenal Hyperplasia cases?

Answer 35

21-hydroxylase

Question 36

What does the corpus luteum secrete?

Answer 36

Progesterone

Question 37

A healthy 36-year-old man being assessed for infertility is found to have a low sperm count of 10 million/mL (normal >15 million). He has no past medical history or drug history of note. What blood result could explain this finding?

Answer 37

reduced FSH levels

Question 38

Which is the site of androgen production?

Answer 38

Leydig cell

Question 39

Sertoli cells are responsible for what?

Answer 39

supporting the germ cells with spermatogenesis

Question 40

Leydig cells are responsible for what?

Answer 40

producing testosterone and other hormones in response to Luteinising hormone

Question 41

Which structure provides the majority of the ejaculate volume?

Answer 41

Seminal vesicles

Question 42

Seminal vesicles are responsible for what?

Answer 42

production fo the majority of the ejaculate

Question 43

The epididymis is what in the male reproductive health?

Answer 43

collecting duct at the posterior of the testes which leads to the Vas deferens