Search
menstrual (estrous) cycle
Clinical significance:
- normal length 25-35 days
- in women < 40 years of age, menstrual cycle < 25 days or > 35 days likely anovulatory [1]
Physiology:
Day event
0 menses
2 ... day 2: begin follicular phase
6
10
.....- day 13: estradiol peak
14 ... day 14: FSH & LH surge, begin luteal phase, progesterone secretion
20
24
28 ... menses
GnRH:
1) increased frequency of GnRH pulsatile secretion early in follicular phase
2) abrupt change in frequency of GnRH pulses during late luteal phase as levels of sex steroids & inhibin A secretion wane
3) lowest levels of GnRH 10 days after mid-cycle LH surge
Estradiol:
1) mid-cycle surge
a) begins day 8 or 9
b) peaks at day 13
c) minimum at day 16
2) secondary rise & plateau during luteal phase in parallel with progesterone
Follicular phase:
1) dominant follicle development is coordinated with atresia of remaining follicles
2) dominant follicle reaches size of 1.5-2.5 cm at the time of ovulation
3) gradual decline in FSH as follicular phase progresses
4) rising estradiol secreted by dominant follicle evokes LH surge from pituitary
5) LH surge ruptures dominant follicle, releasing mature oocyte
Luteal phase:
1) corpus luteum forms from remnants of ruptured follicle
2) corpus luteum secretes progesterone, estradiol & inhibin A resulting in slowed GnRH pulse
3) temporary predominance of FSH over LH for 3-7 days in late luteal phase that recruits a new wave of folliculogenesis in the ovaries
Related
menopause
menorrhagia
menstrual disorder
menstruation (menses, menstrual period)
General
physiologic process
References
- Medical Knowledge Self Assessment Program (MKSAP) 11, 17, 19.
American College of Physicians, Philadelphia 1998, 2015, 2022
Components
luteolysis