Menstrual cycle hormone physiology (follicular, ovulation, luteal phases)
Core concept
- Two cycles running together: ovarian (follicular -> ovulation -> luteal) and endometrial (proliferative -> secretory)
- Hypothalamic GnRH pulse frequency is the master control
- Fast pulses -> LH; slow pulses -> FSH
- Cell division of labour - the two-cell, two-gonadotrophin model
- LH -> theca cells -> androgens (androstenedione, testosterone)
- FSH -> granulosa cells -> aromatase -> converts those androgens to oestradiol
- Same axis in the male: LH -> Leydig -> testosterone; FSH -> Sertoli -> spermatogenesis + inhibin B
- *Oestradiol feedback switches from negative to POSITIVE above ~700-1100 pmol/L sustained for ~36-48 h* - this is what triggers the LH surge
3 more sections, plus exam facts
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