Clinical (Week 5 - Calcium and Reproduction) Flashcards
Where are oestrogens synthesised?
Ovaries:
- Granulosa
- Theca cells
Corpus luteum
What does LH stimulate the granulosa cells to produce?
Pregnenolone
What diffuses from the granulosa cells to the adjacent theca cells and what does this cause?
Pregnenolone
Causes theca cells to express:
- 17,20-lyase (also known as 17α-Hydroxylase)
- 3β-HSD
What happens when the theca cells express the enzymes in response to pregnenolone?
Pregnenolone is converted to DHEA:
- By 17α-hydroxylase
DHEA is converted to androstenedione:
- By 3β-HSD
What other function does 3β-HSD have?
Converts pregnenolone to progesterone
What are the three types of naturally occurring oestrogen in the body?
Oestrone (E1)
Oestradiol (E2)
Oestriol (E3)
What happens to most androstenedione?
Returns to granulosa cells:
- Converted to oestrone (E1) by aromatase
What function does 17β-HSD have?
Converts oestrone (E1) to Oestradiol (E2) (Also converts Androstenedione to testosterone)
What enzymes does FSH increase the expression of?
Aromatase
17β-HSD
(Both from the granulosa cells)
Where else can oestrogens be synthesised?
Aromatase is expressed in fat and bone:
- Peripheral production of Oestrone (E1)
Where is progesterone synthesised and by what enzyme?
Made from pregnenolone by 3β-HSD in:
- Corpus luteum - Placenta (during pregnancy) - Adrenal glands
Why is progesterone made in the adrenal glands?
Step in androgen and mineralocorticoid production
During the following stages, what products are mainly made from pregnenolone:
- Follicular maturation
- Following ovulation (Luteal phase)
Follicular maturation:
- Oestradiol (E2)
Luteal phase:
- Progesterone
What is oligomenorrhoea?
Reduced period frequency to less than 9/year
OR
Having a menstrual cycle > 35 days
What is primary amenorrhoea?
Failure of menarche by 16 years of age
What is secondary amenorrhoea?
Cessation of periods for >6 months:
- In a woman who previously menstruated
What are the two physiological causes of amenorrhoea?
Post-menopausal state
Pregnancy
What can cause primary amenorrhoea?
Turner’s Syndrome (45, XO)
Kallman’s Syndrome
A 19 year old woman presents concerned that she hasn’t started menstruating. She has also noted that her breasts have hardly developed. On examination you notice she has no sense of smell (anosmia). You decide to test her pituitary hormones and discover a lack of LH and FSH.
Kallman’s Syndrome
What ovarian problems may cause secondary amenorrhoea?
PCOS
Premature ovarian failure
Which of these does not cause hypothalamic dysfunction and therefore does not cause secondary amenorrhoea:
- Weight loss
- Over exercise
- Poor sleep
- Stress
- Infiltrative disease
Poor sleep
What pituitary problems can result in amenorrhoea?
Increased PRL
Hypopituitarism
Flushing, reduced libido and dyspareunia are signs of what?
Oestrogen deficiency
What is dysparenuia?
Difficult or painful sex