Ovulatory disorders, hormone release and fertilisation Flashcards
What hormone does the hypothalamus release that causes the anterior pituitary to release gonadal hormones?
Gonadotrophic releasing hormone.
What are the gonadal hormones?
Luteinising hormone and follicle stimulating hormone.
What action does follicle stimulating hormone have and where does it act?
Follicle stimulating hormone acts on the ovaries to cause maturation of the primary follicles to secondary follicles.
What hormone is released as the primary follicle becomes the secondary follicle?
Oestrogen.
In low concentrations, oestrogen has…..effect
An inhibitory effect on LH.
A stimulatory effect on FSH.
In high concentrations, oestrogen has…. effect
A stimulatory effect on LH.
An inhibitory effect on FSH.
Name the two phases of menstruation
Follicular phase and luteal phase.
Describe the follicular phase
Follicle develops from the primary follicle to a secondary follicle releasing oestrogen. This causes LH to be suppressed and FSH to slightly rise at first. As levels of oestrogen increase, FSH concentration falls and LH increases. The spike in LH causes ovulation of the most mature follicle.
Describe the luteal phase
After ovulation, LH levels dip. The follicle is now a dead follicle known as a corpus luteum. The corpus luteum secretes several hormones as it is converted to the corpus albicans. These include progesterone, oestrogen and inhibin. Progesterone inhibits the release of GnRh from the hypothalamus, inhibin prevents the release of FSH and oestrogen levels are still detectable. Once the corpus luteum becomes the corpus albicans- these hormones are no longer released allowing GnRH to rise again and a new cycle to start.
What are the actions of progesterone in the luteal phase of menstruation?
Stimulates endothelial growth.
Inhibits GnRH release.
What is the function of theca cells
During the follicular phase of growth- these cells are recruited around the follicle. They release androgens.
What is the relationship between theca cells and granuloma cells?
Granuloma cells produce aromatase which converts the androgen produced by theca cells to oestrogen.
When is HCG released?
The follicle will release this if it has been fertilised.
What does HCG do?
Maintains the corpus luteum- after 6 weeks the placenta takes over this role.
What is amenorrhoea?
Absent menstruation
What is oligomenorrhoea?
Cycle greater than 35 days
Less than 9 periods per year
Primary causes of amenorrhoea
Failure of menarche by the age of 16
Causes include- congenital issues e.g. Turners syndrome, Kallmann’s syndrome
Secondary causes of amenorrhoea
Cessation of periods for >6 months in an individual who has already menstruated.
Causes include- PCOS, POF, uterine problems, hypothalamic dysfunction (weight loss, excessive exercise, stress), hypopituitism, high prolactin.
What does prolactin do?
Stimulates formation of breast milk. Often seen in pregnant women.
WHO classification of amenorrhoea
Group 1- hypothalamic pituitary failure
Group 2- hypothalamic pituitary dysfunction
Group 3-ovarian failure
Hypothalamic pituitary failure is also known as
Hypogonadal hypogonadism.
What is hypogonadal hypogonadism
Means the hypothalamic pituitary axis is not produced the gonadal hormones meaning the gonads themselves (ovaries, testes) cannot produce the appropriate hormones (oestrogen, testosterone)
What would the levels of FSH, LH, prolactin and oestrogen be like in a patient with hypogonadal hypogonadism
Low FSH and LH
Meaning low oestrogen
Normal prolactin
Causes of hypogonadal hypogonadism?
Stress Excessive exercise Anorexia Brain/pituitary tumours Head trauma Kallmanns syndrome Drugs (steroids/opiates)
Management of hypogonadal hypogonadism?
Stabilise weight
Pulsatile GnRH release if hypo hypo
Or gonadotrophin daily injections (FSH and LH)
Ultrasound monitoring
Describe hypothalamic pituitary dysfunction
Normal gonadotrophin levels
Normal LH and FSH
Normal oestrogen however oligo/amenorrhoea
What causes hypothalamic pituitary dysfunction?
Empty sella- small or absent pituitary
PCOS
Describe ovarian failure
High levels of gonadotrophins (FSH, LH)
Low oestrogen levels
Causes of ovarian failure
Premature ovarian failure
In females, what characterises hypogonadism?
Low levels of oestrogen