LUFS – ‘Luteinised Unruptured Follicle Syndrome’ is a condition where nearly everything works as it should:
- The dominant follicle develops as normal
- There’s a normal luteinising hormone (LH) ‘surge’
- The follicle is ‘luteinised’ as it should be
- However the follicle doesn’t rupture and release an egg!
So there’s no possibility a pregnancy that cycle, and the unruptured follicle (with egg) remains in the ovary and alters the hormonal balance of following cycles. In normal cycles the LH surge acts to:
- Detach the egg from the lining of the dominant follicle
- Alter the structure of the follicle wall
- Rapidly increase the amount of fluid in the dominant follicle
- Trigger the egg’s release from the follicle
- Start the development of the corpus luteum from the ruptured follicle
In LUFS all of these things happen except the egg’s release from the follicle, and while the dominant follicle normally becomes a corpus luteum and produces large amounts of progesterone for about two weeks (except in pregnancy), with an egg inside it turns into a “functional” cyst that usually lasts about 6 weeks before bursting. During this time the cyst still behaves like a gland and produces enough progesterone and estrogen to alter the hormone levels of following cycles which prevents a pregnancy.
Although LUFS attracts little attention it probably prevents lots of women getting pregnant, and it’s so effective that drug companies have looked into developing a contraceptive that mimics LUFS as it would avoid many of the unwanted side effects of the oral contraceptive pill.i The first phase of cycles are perfectly normal, and even the second phases of LUFS cycles usually seem to be normal, because the luteinised follicle produces enough progesterone to produce a luteal phase of a roughly normal length. Most women believe all’s well because:
- Their cycle has two distinct temperature phases
- There’s a “false positive” of ovulation from the ‘LH surge’ with ovulation prediction kits
Detecting LUFS isn’t easy, but there are subtle differences to normal cycles:ii