Scrub the day and watch the loop: FSH recruits, oestradiol rises and flips the feedback, LH surges, the corpus luteum makes progesterone, and the lining follows. Then break the loop and see what the clinic sees.
FSH LH Oestradiol ProgesteroneSchematic curves in relative units, not assay values.
The ovary and the lining on the same day axis as the hormones above. Click a follicle to jump to its day. Sizes are schematic.
Proliferative endometriumProliferative endometrium: straight glands under oestrogen, before ovulation.Secretory endometriumSecretory: corkscrew glands under progesterone
Endometrium
11 mm
Basal temp
36.77 C
Follicle
22 mm
FSH
58%
LH
86%
Oestradiol
78%
Progesterone
10%
FSH recruits the cohort; the dominant follicle's oestradiol suppresses FSH then, at a sustained high level, triggers the LH surge; the corpus luteum makes progesterone for about 14 days and regresses.
A day-21 progesterone is drawn in a 28-day cycle. What is it for?
Why does high oestradiol on day 12 to 13 cause an LH surge when lower oestradiol on day 7 suppressed LH?