4/9 PCOS: e-Lecture Flashcards
What is this?
How is it sometimes described?
Polycystic ovary.
Can be described as a “ring of pearls”: multiple small peripheral follicles with a very dense stroma/theca cells in the interior.
PCOS is associated with what 4 findings?
- Chronic anovulation (irregular menses, dysfunctional uterine bleeding, amenorrhea)
- Androgen excess (may be male pattern facial hair)
- Physical characteristics of obesity and androgen excess
- Physical features of insulin resistance (acanthosis nigricans)
(all these are found to variable degrees)
Describe the physical manifestations of PCOS related to androgen excess.
- Hirsutism: male hair patterns: face, chest, abdomen, lower back)
- Acne
- Male pattern hair loss
PCOS: what is the typical body habitus?
75% are obese
But there is a “lean” form of PCOS also
Why do PCOS patients have high levels of androgens?
Increased release of LH from the pituitary –> overstimulation of the ovarian theca cells –> high levels of androgens.
Review: what is the sequence of events in the uterus that yields endometrial shedding in the normal ovulatory cycle?
- Estrogen primes the endometrium - it builds up
- Progesterone then stabilizes/compacts it
- Withdrawal of Progesterone and Estrogen
- Universal endometrial shedding
In adolescents who are not ovulating regularly, how do they have menstrual bleeding?
Normal adolescent oligo-ovulatory cycles:
Menstrual bleeding (“estrogen withdrawal bleed”) occurs during the spontaneously operative negative feedback system between estrogen and FSH.
However, for ovulation to occur, estrogen levels must peak for a SUSTAINED period of 2 days at the end of the follicular phase for (+) feedback to occur (for LH surge). In btwn the start of menstruation and regular ovulation, the estrogen isn’t high enough for long enough to cause the LH surge that is necessary to induce ovulation.
A patient with PCOS will have higher or lower average levels of LH than a normal patient?
FSH?
LH: PCOS patient will be higher than normal
FSH: PCOS patient will be slightly lower and will not have the FSH bump at day -14.
(PCOS = yellow and red lines)
In PCOS, the increased LH is due to what?
increased pulsatile GnRH (both amount and frequency)
PCOS: what causes the polycystic ovaries?
A number of causes:
- slightly decreased FSH is enough to recruit follicles, but the **lack of FSH blip **prevents the recruitment of a dominant follicle from the cohort
- increased ovarian androgens -> follicular atrophy
- elevated LH -> a dominant follicle is discouraged
-insulin resistance -> increases androgen production at the ovary
What is the direct result of not having an FSH ‘blip’ at day -14?
The FSH blip normally stimulates one follicle to emerge from the cohort and become dominant.
Without the blip, you are unlikely to get a dominant follicle.
Even if a follicle were to try to emerge as dominant, what (besides the lack of FSH blip) is discouraging this?
High ovarian androgen concentration (in the micro-environment of the ovary) prevents one follicle from emerging from the cohort.
Insulin resistant also plays a role: unknown mechanism.
LH stimulates the theca cells to produce what?
more androgens
in PCOS you have increased LH –> increased androgens
What is the fundamental problem causing PCOS?
nonfunctional feedback in the HPO axis.
prevents spontaneous negative and positive feedback to endogenous hormones.
Patients don’t often ovulate, have long stretches of unopposed estrogen, thus endometrial proliferation.
Given that PCOS patients have unopposed estrogen, what is their bleeding pattern like?
Why is this?
Endometrium grows unabated until it is really unstable. It’s not compacted due to lack of progesterone. Eventually it will become excessively unstable and will spontaneously shed - might bleed for 1-3 weeks and very heavy bleeding.
If this is the pattern of normal negative feedback for FSH and estrogen, what does the pattern look like for a PCOS patient?
(Yellow dots: endometrial growth.
Red arrows = menses)
PCOS: lacks pulsation, no feedback. If estrogen rises, FSH/LH do not lower.
FSH is tonically elevated; stimulates multiple follicles (but rarely enough FSH for one follicle to break out of the pack and become dominant)
(Yellow dots: endometrial growth.
Red arrows = menses)
In this depiction of PCOS uterine activity, what is happening at each stage?
left: long term unopposed estrogen influence on endometrium. leads to thickened, unstable endometrium.
center: erratic shedding of unstable endometrium - prolonged heavy menses.
right: after prolonged menses, incomplete shedding to basal layer.
PCOS: the big picture.
walk through the steps related to high LH levels.
Top: desuppressed arcuate nucleus via increased GnRH pulsatility. Widens the difference between LH and FSH levels -> higher LH, lower FSH.
High LH stimulates increased ovarian androgens. Androgens knock off follicles as they are developing (follicular atresia). Leads to anovulation and unopposed estrogen.
Increased ovarian androgens -> high peripheral aromatization (testosterone -> incr estrogen). Helps to widen the GnRH pulse frequency.
Increased ovarian androgens -> decrease levels of Sex Hormone Binding Globulin (SGBH) in liver. -> higher free androgen -> hirsutism, acne, etc.
PCOS: the big picture.
walk through the steps related to low FSH levels.
Low FSH means that multicle follicles mature, but there is not enough FSH to allow one to dominate.
Bottom line: no ovulation.
PCOS big picture again: if a PCOS patient is given birth control, which points of this cycle are affected?
Birth control will increase SHBG as well as suppress GnRH pulsatility and suppress androgen production.
What is the role of insulin resistance in PCOS?
At which points of the cycle does it have an effect?
Acts at multiple levels:
-Hypothalamus: increased GnRH pulsatility
Hypothalamus: Stimulates appetite
- Ovaries and adrenals: increased production of androgens
- Liver: decr SHBG levels
