11 - The gonads II

Question 1

Where are androgens produced?

Answer 1

in the gonads and adrenal glands

Question 2

What type of hormone are androgens?

Answer 2

steroid hormones

Question 3

What specific plasma protein does transport a large majority of androgens?

Answer 3

sex hormone binding globulin (SHBG)

Question 4

What are the precursors of oestrogens (17β-oestradiol)?

Answer 4

• oestrone
• testosterone
• androstenedione

Question 5

What is the main effect of the negative feedback mechanism of testosterone?

Answer 5

LH levels decrease

Question 6

What effect does inhibin have?

Answer 6

decreases FSH levels

Question 7

MENSTURAL CYCLE:

Give a summary of the changes in hormones in the early follicular phase

Answer 7

• low oestrogen and progesterone levels
  negative feedback - increase in GnRH, LH and FSH
• LH and FSH stimulates the development of some of the follicles in the ovary

Question 8

MENSTURAL CYCLE:

Give a summary of the changes in hormones in the early follicular phase

Answer 8

• low oestrogen and progesterone levels
  negative feedback - increase in GnRH, LH and FSH
• LH and FSH stimulates the development of some of the follicles in the ovary

Question 9

MENSTURAL CYCLE:

Give a summary of the changes in hormones in the early-mid follicular phase

Answer 9

• no further increase in FSH and LH
• oestrogen levels rise dramatically
• no change in progesterone

Question 10

MENSTRUAL CYCLE: mid-follicular phase

What cells have the receptors for LH and FSH in the ovaries?

Answer 10

thecal cells = LH receptor

granulosa cella = FSH receptors

Question 11

MENSTRUAL CYCLE: mid-follicular phase

What is the result of FSH and LH binding to their corresponding receptors in the ovaries?

Answer 11

• thecal cells respond to LH by producing androgens
• granulosa cells respond to FSH receptors by releasing aromatase
• aromatase converts the androgens to 17β-oestradiol

Question 12

MENSTRUAL CYCLE: mid-follicular phase

What is the positive feedback mechanism of oestrogen?

Answer 12

oestrogens produced from the thrall and granulosa cells will bing to the oestrogen on the receptors on the same granulosa cell (and further stimulates the production of oestrogen)

Question 13

MENSTURAL CYCLE:

Give a summary of the changes in hormones in the late follicular phase

Answer 13

• high oestrogen in the absence of progesterone —–> LH surge
• LH surge is high enough to overcome the FSH negative feedback ——> lesser FSH curve

Question 14

MENSTRUAL CYCLE:

give a summary of what happens in the luteal phase

Answer 14

• (after ovulation) the cells of the follicle collapse and become the corpus luteum
• the corpus luteum still has FSH and LH receptors
• when the androgen levels fall, it there is a rise in FSH and LH
• this stimulates the corpus luteum to produce more oestrogen and progesterone
• negative feedback —–> the levels of FSH and LH decrease
• oestrogen and progesterone levels fall because they are no longer being simulated
• the levels of FSH and LH to rise again

Question 15

Define oligomenorrhoea

What can be the cause?

Answer 15

infrequent menstrual cycles
causes:
- absence of LH surge

Question 16

There are many causes of infertility. Give one

Answer 16

excess prolactin