Cycle Timeline (28-day standard)
| Days | Phase | Key Hormones | Ovarian Event | Uterine Event |
|---|---|---|---|---|
| 1–5 | Menstrual | Low + Low | Follicle begins forming | Endometrium shed |
| 6–13 | Follicular/Proliferative | ↑FSH → ↑Estrogen () | Follicle grows → Graafian | Endometrium proliferates |
| ~14 | Ovulation | LH SURGE (+ FSH surge) | Graafian follicle ruptures | — |
| 15–28 | Luteal/Secretory | ↑Progesterone () from CL | Corpus luteum active | Endometrium = thick, glandular |
| 28 (if no pregnancy) | → Menstruation | drops (CL degenerates) | CL → corpus albicans | Endometrium sheds → day 1 |
Critical Formula Points
- LH surge (not FSH) = ovulation trigger
- Estrogen (from follicle) = endometrial proliferation
- Progesterone (from corpus luteum) = secretory endometrium
- hCG (from trophoblast) = corpus luteum rescue in pregnancy