physiology of menstruation, menopause, puberty Flashcards
Describe the physiology and endocrinology of the menstrual cycle (the axis)
the hypothalamus produces GnRH
GnRH stimulates the anterior pituitary to produce LH and FSH
LH acts on theca cells of ovaries causing them to produce androgen
FSH acts on granulosa cells causing them to express an enzyme that converts the androgens to oestrogen. Also produce inhibin
when O is low or with P it can inhibit the axis to maintain constant FSH and LH levels
when O is high (in absence of P) it can stimulate - positive feedback for ovulation
inhibin inhibits FSH selectively
what are the 3 phases of the ovarian cycle?
follicular
ovulation
luteal phase
what happens in the follicular phase of the ovarian cycle?
this marks the start of the cycle - LH and FSH and O+P are all low. less negative feedback so LH and FSH slowly rise. O slowly rises and the follicles slowly grow
one follicle eventually dominates and the rest regress
now there is a high level of O and low P and thus positive feedback of the axis - LH surge
describe the physiology behind ovulation
This starts with the LH surge which induces the follicle to rupture and oocyte to mature. the oocyte is the released (ovulation) and is transported to the fallopian tubes by fimbria
can be fertilised for up to 24 hours within the fallopian tube
the LH surge also causes granulosa cells to become lutinised (remaining follicle now called corpus luteum) and express LH receptors. LH now causes the granulosa cells to produce progesterone.
P starts to rise and can act with O to maintain axis by negative feedback (stalls axis in anticipation for fertilisation)
what is the luteal phase of the ovarian cycle?
corpus luteum continues to secrete O +P to maintain conditions for fertilisation/ implantation until the placenta can take over.
at 14 days the corpus luteum spontaneously regresses (unless hCG from pregnancy maintains it for up to 4 months)
once corpus luteum regresses, drop in O and P and so less negative feedback so LH and FSH can again continue to slowly rise.
what are the phases of the uterine cycle?
proliferative phase
secretory phases
menses
what happens in the proliferative phase of uterine cycle?
this runs alongside the follicular phase of ovarian cycle.
Oestrogen prepares for fertilisation/ implantation
- fallopian tube maturation
- endometrium thickening (functional layer grows, basal stays the same),
- increases growth and motility of myometrium
- thin alkaline cervical mucus - sperm friendly
what happens during the secretory phase of the uterine cycle?
alongside luteal phase of ovarian cycle
progesterone further prepares the endometrium
- glandular secretory form
- further thickening of myometrium
progesterone also promotes thick acidic cervical mucus - prevent polyspermy. also changes to mammary tissue
describe the physiology behind menses?
corpus luteum regresses and O and P reduced
P can no longer maintain endometrium so it sheds and bleeds.
- lack of P leads to prostaglandin release which casues:
- spiral artery vasospasm nd ischaemic necrosis of superficial layers of endometrium- increased myometrial contractions
what are the physiological mechanisms to stop bleeding in menses?
spiral artery vasospasm
platelet plugging
repairing of endometrium
what is classed as normal frequency, frequent and infrequent menses?
normal - around 28 days (24-32)
frequent - <24 days
infrequent . >38 days
what is classed as a normal duration, short and prolonged duration of menses
5 days = normal
>8 days = prolonged
<4.5 days = short
what is the average blood loss in menstruation. what defines menorrhagia, and oligomenorrhagia?
average = 40 ml
menorrhagia >80 ml
light <5ml
when is menarche usually?
between 11-15 yrs
when is menopause usually?
between 45 -55
what factors affect menstrual blood loss
age
hereditary
parity
uterine pathology
what defines menopause and pre-menopause?
pre-menopause: defined as from the beginning of symptoms of menopause to the start of having no periods for 12 months. in this part, periods become less regular
menopause - the absence of periods for 12 months
what are the hormonal changes in menopause?
reduced oestrogen from ovaries results in less negative feedback and thus rise in LH/FSH
reduced sensitivity of ovaries to LH/FSH so oestrogen remains low (this is because fewer follicles and thus less binding sites = loss of ovarian follicular activity)
increased number of anovulatory cycles
inhibin is increased and so FSH rises more so than LH
progesterone is also low
how is menopause diagnosed?
history - >45 years old and symptoms
blood test - high FSH
- FSH >40ml U / ml
- only need this diagnosis if <45 and menopause suspected
- not reliable if on POP/COCP or HRT
LH, O and P not routinely used for diagnosis but expect LH to be high and O and P to be low
what are the symptoms of peri menopause?
hot flushes - usually head, neck and chest. associated with peripheral vasodilation and transient rise in body temperature
dyspareunia - loss of oestrogen results in vaginal atrophy and thining of myometrium. also dryness.
urinary incontinence - atrophy of bladder and urethra
(also increased UTIs)
irregular vaginal bleeding - small amount of O causes endometrium to grow, no P and thus cant be maintained so break through bleed every 14 days. (also some normal ovulation can cause bleeding)
fracture/ osteoporosis (oestrogen inhibits osteoclasts)
ischaemic heart disease (oestrogen is protective)
irritable, depression, reduced concentration
loss of libido
how is menopause managed?
give advice of what symptoms to expect, long term health implications of menopause and advantages/ disadvantages of HRT
HRT
osteoporosis prophylaxis
what HRT can be offered in menopausal women?
types: upposed O, O and P (continuous or biphasic)
delivery method: tablet, transdermal path, vaginal ring
what are the risks of HRT?
breast cancer endometrial cancer and ovarian cancer (for unopposed O) DVT risk heart disease ischaemic stroke uterine bleeding adverse lipid profile and risk of T2D
but bone protection
what osteoporosis protection can be given in menopause
bisphosphonates, exercise, ADCAL, raloxifene (SERM)
