Gonad funciton

Question 1

What are the gonadotrophins?

Answer 1

Hormones secreted by the anterior pituitary, luteinizing hormone (LH) and follicle stimulating hormone (FSH). To aid develivering the gonadal function

Question 2

How is LH and FSH released?

Answer 2

Controlled by GnRH. Release occurs in a pulsatile manner. Where FSH release at low frequency pulses, whilst LH occur at high frequency pulses.

Question 3

What is the strucutre of LH and FSH?

Answer 3

Glycoproteins with 2 subunits. Made up of a common alpha unit and an unique beta subunit.

Question 4

Function of female gonads?

Answer 4

Ovaries functions for ovum production and production of sex steroids (androgens and oestrogens)
- Function stimulated by LH and FSH

Question 5

What cells mediate the gonadal function (female)?

Answer 5

Theca cells, granulosa cells and corpus luteum

Question 6

What do the different cells secrete (female)?

Answer 6

Theca - androgens (androstenedione and testosterone)

• Granulosa cells utilise theca secretions to make oestradiol (E2)
• Granulosa cells also secrete inhibins which has negative feedback on FSH but not LH.
• Corpis luteum switches production of progesterone from E2 to act on breast to stimulate grandular development
• Corpus luteum further tests: endometrium, stimulates its secretory and vascular activity, to prepare for implantation of embryo

Question 7

What happens if there is no implantation of embryo in the corpus luteum?

Answer 7

Simply degrades and stop secreting progesterone causing menstruation

Question 8

Describe the role of LH (female)

Answer 8

Acts to induce ovulation. Stimulate theca cells to produce steroids, androstenedione and testosterone that diffuse inot the granulosa cell for E2 convertion
- Prepares for uterine implementation of fertilised oocyte as follcicle turns into corpus luteum

Question 9

Describe the role of FSH (female)

Answer 9

• Stimulate growth of immature follicles, maturing one follucle before ovulation

Question 10

Describe the menstrual cycle

Answer 10

Follicular phase

• Begins with FSH stimulating granulosa cells to produce oestrogen for follicular maturation, negatively feedback on LH
• oestrogen causes more oestrogen release by granulosa cells
• Rise in E2 feedsback on GnRH to increase pulse frequency
• Surge in LH causes luteinisation of granulosa cells enabling progesterone produciton (luteal phase)
• When the LH falls the cycle begins again

Question 11

How is the gonadal secretion regulated?

Answer 11

By inhibin and activin.

• Inhibin a glycoprotein inhibits GnRH release and FSH production
• Inhibin peaks midphase
• Activin, a dimer of inhibin beta subunit AB/A/B, oppose inhibin to stimulat eFSH secretion.
• Activin, enhances androgen synthesis under LH control

Question 12

What is anti-mullerian hormone (AMH)?

Answer 12

• structurally similar to activin and inhibin
• secreted by granulosa cells following transition from the primordial to primary follicular stage and continues until the follicles reach the antral stage

Question 13

When is AMH high?

Answer 13

Remains low at birth but rises with age until puberty.

- Decreases with time, with an accerlerated decrease in menopause

Question 14

What does the concentration of AMH tell you?

Answer 14

Concentration of AMH is proportional to egg maturation potential/ovarian reserve

Question 15

When can AMH measurement be particularly important?

Answer 15

See potential response to IVF

Question 16

What are some disorders of AMH?

Answer 16

• Low in menopause

- High in polycystic ovarian cancer

Question 17

What biochemical change occurs in menopause?

Answer 17

Hypogonadotrophic hypogonadism
- increase in FSH and LH but decreased E2. This occurs as the pituitary secretes hormones continuously stimulate the ovary, but it has failed.

Question 18

What is the gonadal function in males?

Answer 18

Testes have functions to produce testosterone and act as a site for spermatogenesis (occurs in the seminiferous tubules).
- stimulated by gonadotrophins

Question 19

Why is the testes external organs?

Answer 19

REquire lower temp to carry out function

Question 20

What different cells exist in the testes?

Answer 20

Seminiferous tubules

• Germ cells function to develop sperm via spermatogenesis
• Epithelium, Sertoli cells, support the germ cell development by secreting inhibin and AMH

Leydig cells
- Leydig cells, found between seminiferous tubules, act to secrete testosterone and other androgens.

Question 21

Regulation of in testes?

Answer 21

• FSH stimulate sertoli cells to produce inhibin which negatively feedback on pituitary and hypothalamus
• LH stimulates production of testosterone which negatively impacts the pituitary release and hypothalamys somewhat

Question 22

What is AMHs function in males?

Answer 22

• Important functions in early male reproductive development
• Inhibit the development of the female reproductive tract, specifically the Mullerian ducts
• Actions of AMH combined with testosterone allows the development of the wolffian duct

Question 23

When is AMH highest in males?

Answer 23

During puberty >1000pmol/L

Question 24

Why is a testosterone immunoassay problematic?

Answer 24

• Sensitive enough men, but children and women require mass spec
• potential cross reactivity with DHEAS and synthetic Oral Contraceptive Pills, which causes spuriously raised testosterone
• Drug therapies need to be reassed: norethisterone will produce a positive interference for females with dysmenoregia
• Transgender - need to account for testosterone replacement therapy