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Luteinised Unruptured Follicle Syndrome (LUFS) is a subtle variation of regular cycles that effectively prevents pregnancy. The condition isn’t that well known, partly because nearly everything in menstrual cycles 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 or release an egg!

The egg in the unruptured (but luteinised follicle) remains in the ovary, which not only prevents pregnancy in that cycle, it also alters the hormonal balance of the following cycles because it becomes a “functional” cyst.

Normal cycles

In regular cycles, the surge of luteinising hormone (LH) has a dramatic action:

  • The egg detaches from the lining of the“dominant follicle”
  • The structure of the follicle wall alters, and a blister forms on the surface
  • Fluid levels rapidly increase within the dominant follicle
  • The blister bursts, and the egg is released (ovulated) from the follicle
  • The LH stimulates the empty ruptured“dominant follicle” to transform into a corpus luteum


Release of an egg from a follicle

Because an egg remains in the follicle in LUFS cycles, the corpus luteum develops abnormally, but it still manages to produce progesterone for about two weeks and is then a “functional cyst” that usually lasts for about six weeks. Functional cysts are filled with fluid, and the larger they are, the more likely they are to cause physical symptoms, which are usually:

  • Pain in the lower abdomen and pelvis
  • Pain with intercourse
  • Changes to the length and nature of the period


The dominant follicle and the corpus luteum are temporary glands that produce sex hormones, and functional cysts produce progesterone and estrogens at levels that are lower than normal for either of these glands. However, the hormone levels are high enough to disrupt following cycles and prevent pregnancies.

Although few people know about LUFS, it probably prevents many pregnancies, and it’s so effective that drug companies have looked into developing contraceptives that mimic LUFS as they avoid many of the unwanted side effects of the oral contraceptive pill. i

Detecting LUFS

Spotting LUFS isn’t easy as:

  1. The first phase of cycles seems perfectly normal
  2. The second phases of LUFS cycles usually appear normal as they’re usually about the right length

Most women believe all’s well because:

  • Their cycle has two distinct temperature phases
  • Ovulation prediction kits give a “false positive” of ovulation from the “LH surge”

However, there are subtle differences to normal cycles: ii

  • The dominant follicle grows slower than usual iii
  • The progesterone rise after luteinisation is delayed until about 42 hours later
  • Progesterone levels in the middle of the luteal phase are lower than usual
  • The blood flow in the follicle after the LH surge is low
  • BBT charting shows different temperature changes in the luteal phase
  • Ultrasound “follicle tracking” reveals no hole (stigma) in the dominant follicle after ovulation, which confirms LUFS

Clomid and LUFS

Clomiphene citrate (Clomid) significantly increases the chances of LUFS. While Clomid undoubtedly triggers ovulation for many women, it also increases the chances of LUFS the more it’s used. Clomid works by stimulating the anterior pituitary to produce more FSH and LH during the first few days of the menstrual cycle. When Clomid is given alongside IUI there’s evidence that many women who previously had regular cycles developed LUFS: iv

  • 25% had LUFS in the first cycle
  • 56.5% had LUFS in the second cycle
  • 58.9% of women who had a third cycle had LUFS

Of course, a percentage of the women got pregnant each cycle, but of the women who had LUFS in the first cycle:

  • 78.6% had LUFS in the second cycle
  • 90% had LUFS in the third cycle

This research backs up the theory that the main issue with LUFS is concerned with follicle development and the hormone balance in the follicular phase of the cycle, rather than a problem with the LH surge that triggers ovulation. v

Clomid and Fertility Profiles

Clomid is a “heating” drug that causes flushes, irritability, and drying of the fertile mucus. It also reduces E2 (estradiol, a crucial estrogen) that stimulates the womb lining to grow. As a result there’s a clear link between Clomid use and women having thinner endometrial linings, which is more of an issue for some women than others. vi vii viii ix

Women with Fluids or Cold PPFs usually respond well to Clomid because of its heating action.

Hot (Energy and Blood PFPs) tend to respond poorly to Clomid because:

  1. It reduces the amount of fertile mucus, which makes it difficult for sperm to enter the womb
  2. It reduces the depth of the womb lining and lowers implantation success

Clomid is also linked to abnormalities in Fallopian tube structure and function, which delay embryo and sperm movement and increase the chances of ectopic tubal pregnancy. x