Luteinized Unruptured Follicle

Common Fertility Problems
Key Points

  • LUF happens when a follicle doesn’t release an egg, despite being stimulated by LH.
  • Medication can resolve LUF in some cases.
  • When medication doesn’t trigger ovulation, IVF can be used.

What is Luteinized Unruptured Follicle?

When a threshold level of 2.5 times the baseline amount of LH needs is reached, ovulation happens. This is the release of the egg from the ovarian follicle, allowing it to be fertilized by sperm. Luteinized unruptured follicle occurs when the follicle fails to rupture and release the egg after stimulation by LH. It occurs in more than 50% of women with unexplained infertility. It is also more frequent in women with endometriosis.


LUF syndrome can be suspected in women who after ovulation, the plasma FSH concentrations remain elevated for a few days.

Diagnosis is made with:

  • Ultrasound scans, inspecting the ovaries during ovulation phase. These scans show that the follicle matures, but the dominant follicle fails to rupture.
  • Laparoscopy between days 15 and 20 of the cycle, for collection of peritoneal fluid and analysis of steroid hormone concentrations (progesterone and 17β-estradiol levels).

Types of LUF

Two distinct types of LUF syndrome were identified:

  • Mature follicle LUF, in which release of an egg was not demonstrated after a follicle attained maturity (serum estradiol reached 200 pg/mL while serum progesterone remained less than 2.5 ng/mL)
  • Premature luteinization LUF, where the serum progesterone increased above 2.5 ng/mL before follicular maturation was attained.


  • The use of either hCG alone or hCG in combination with hMG in a single injection at the time of follicular maturation successfully corrected mature follicle LUF in 21 of 46 patients (46%).
  • Ovulation-inducing drugs plus hCG or hCG and hMG corrected LUF in 24 of 25 patients (96%).
  • Clomiphene citrate proved inferior to hMG in that it corrected LUF in 3 of 25 patients (12%) versus 12 of 22 patients (95%) who had undergone hMG therapy.
For premature luteinization, speeding up follicular maturation with gonadotropin therapy is effective. Upon failure of this technique, the more costly endogenous gonadotropin suppression followed by hMGcan be employed. Intercourse or intrauterine insemination can be times after medication.

If medication fails to trigger ovulation, IVF is the next step.
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