The simple idea (no memorising)
Run the loop again, but remove ovulation:
The key phrase is "unopposed estrogen" — estrogen with no progesterone to balance it. The lining just keeps thickening until parts of it outgrow their blood supply and break down at random.
A picture for your mind
Imagine a builder who keeps adding bricks but no one ever finishes or furnishes the room. Eventually walls collapse here and there — messy, unpredictable. That's an anovulatory bleed.
Why it matters
This is one of the most important ideas in gynaecology because it links so many things:
- it explains the irregular periods of PCOS (Part 3);
- long‑term unopposed estrogen is what raises the risk of the lining overgrowing — and, eventually, womb‑lining cancer (Part 8).
When you understand anovulation → unopposed estrogen, you're holding a thread that runs through half the book.
Doctors have a checklist for abnormal bleeding
When bleeding is abnormal, clinicians run through a memory aid called PALM‑COEIN — the "PALM" half is structural causes you can see or feel (Polyp, Adenomyosis, Leiomyoma/fibroid, Malignancy), and the "COEIN" half is non‑structural (Coagulopathy, Ovulatory dysfunction, Endometrial, Iatrogenic, Not‑yet‑classified). You don't need to memorise it now — just know a tidy checklist exists so nothing is missed.
Quick check ✅
- Why does no ovulation lead to no progesterone?
- What does "unopposed estrogen" do to the lining over time?
Remember this 🌟
Where we're going next → For many, the cycle's most noticeable feature is pain. Where does period pain come from? Concept 15.