Menstrual Physiology Flashcards
What is the most common cause of secondary amenorrhea?
PREGNANCY!
If a woman gets her period regularly (aka every month), what does this mean?
She is ovulatory!
What is the normal menstrual cycle length?
- every 24-35 days and lasts less than 8 days
What brings on the period?
release of an egg from the ovary!
What will happen 2 weeks after ovulation?
EITHER:
- pregnancy (fertilization)
- period
** What is the 1st half of the menstrual cycle called from an OVARY perspective?
the FOLLICULAR phase
** What is the 2nd half of the menstrual cycle called from an OVARY perspective?
the LUTEAL phase (bc there is a corpus luteum in the ovary producing progesterone).
** What is the 1st half of menstrual cycle called from a UTERINE perspective?
PROLIFERATIVE phase
** What is the 2nd half of the menstrual cycle called from a UTERINE perspective?
SECRETORY phase
** From a steroid perspective, is the 1st half of the menstrual cycle dominated by estrogen or progesterone?
ESTROGEN
** From a steroid perspective, is the 2nd half of the menstrual cycle dominated by estrogen or progesterone?
PROGESTRONE
** Withdrawal of which hormone brings on the menstrual cycle? (TEST QUESTION)
PROGESTERONE!
*so when this goes away, a woman gets her period.
What is the variable phase of the ovarian cycle?
follicular phase (aka as you are growing the follicle) *the second phase (luteal) is FIXED between 12 and 14 days.
So a person with a 35 day ovarian cycle, how long is the luteal phase?
still 12-14 days because it is FIXED
** What is the HPG axis? (MUST MEMORIZE)
hypothalamic-pituitary-gonadal/adrenal axis:
- gonadotropin releasing hormone (GnRH) is produced in the hypothalamus (10 amino-acid peptide hormone) and secreted from 4 different nuclei in the hypothalamus.
- GnRH goes into the portalhypophaseal system, which stimulates the gonadotropes (cells in the ANTERIOR PITUITARY).
- anterior pituitary cells (gonadotropes) produce FSH and LH (both peptide hormones)!
- FSH and LH stimulate the FOLLICULAR growth of the ovary!
- In response to FSH, the ovary will produce ESTROGEN, which will stimulate the lining of the uterus (the endometrium to thicken in preparation for possible embryo).
- Ovulation stimulates PROGESTERONE production, and if she becomes pregnant, she will continue to make progesterone!
- If she does not get pregnant, progesterone goes away and she gets her period.
What does follicle mean in laymen’s terms?
just a fancy word for egg “sack”
*each follicle has 1 egg in it, and responds to follicle stimulating hormone (FSH).
In the 1st phase of the menstrual cycle (follicular phase), what happens to GnRH pulsatility?
- a spurt of GnRH occurs every 60-90 mins.
* in the middle it increases to about every 15 mins, which leads to the LH surge.
In the 2nd phase of the menstrual cycle (luteal phase), what happens to GnRH pulsatility?
- a spurt of GnRH occurs every 3-5 hours (aka down-regulated bc it is the embryo driving the process and not the pituitary at this point).
What makes up FSH and LH peptide hormones molecularly?
glycosylated polypeptides composed of an alpha subunit and a beta subunit, each transcribed from different genes.
** What are the 4 hormones that share the alpha subunit?
- TSH
- FSH
- LH
- hCG
*** What is the difference between LH and hCG?
B unit differs by 30 amino acids (this is clinically important)!
*** With respect to LH, when does ovulation occur?
- 36 hours after LH surge (around day 14 of 28 day cycle)!!!
*** So, where is the fertile window?
4 days in the middle of the month!! (days 12-16)!!!!
** What 4 things does FSH do?
- stimulates GROWTH of a cohort of antral follicles and granulosa cell proliferation.
- upregulates FSH and LH RECEPTORS.
- stimulates AROMATASE activity in granulosa cells, stimulating conversion of androstenedione to estradiol.
- stimulates INHIBIN secretion from GC, which functions in negative feedback.