What Is a Luteinized Unruptured Follicle (LUF) and How Does It Affect Fertility?

What Is a Luteinized Unruptured Follicle (LUF) and How Does It Affect Fertility?

When trying to conceive, ovulation is a critical step. However, sometimes an egg may fail to be released even though the follicle has matured and luteinized—a condition known as a luteinized unruptured follicle (LUF). Understanding LUF can help explain unexplained infertility and guide effective treatment options.

What Is a Luteinized Unruptured Follicle?

• The ovarian follicle grows and matures normally.
• Hormonal signals cause the follicle to luteinize (prepare for progesterone production).
• The follicle fails to rupture, so the egg is not released for fertilization.

Even though the hormonal environment may appear normal, no egg is available for conception, which can prevent pregnancy.

How LUF Affects Fertility

• Irregular ovulation: Some cycles may result in no egg release despite normal ovulation signs.
• Unexplained infertility: Couples may struggle to conceive even with timed intercourse or fertility tracking.
• Potential luteal phase issues: Although the corpus luteum forms, hormonal support may not fully compensate for the missing egg.

LUF is often underdiagnosed because standard ovulation tracking methods, like basal body temperature or ovulation kits, may suggest ovulation has occurred when it has not.

Causes of LUF

• Hormonal imbalances, particularly luteinizing hormone (LH) deficiencies
• Ovulatory disorders such as polycystic ovary syndrome (PCOS)
• Endometriosis or pelvic adhesions
• Advanced maternal age, which can affect follicle rupture
• Medications or certain fertility treatments

Diagnosis and Treatment

LUF is typically diagnosed with ultrasound monitoring during the ovulatory period. Treatment strategies may include:

• Ovulation induction medications: Clomiphene citrate or letrozole can help stimulate proper follicle rupture.
• Trigger injections: Human chorionic gonadotropin (hCG) is sometimes used to trigger ovulation.
• Monitoring with assisted reproductive technology: IVF bypasses the need for natural ovulation, retrieving eggs directly from the follicles.

Bottom Line

A luteinized unruptured follicle is an under-recognized cause of infertility that can prevent conception despite regular cycles and ovulation signs. If you experience difficulty conceiving or suspect ovulatory issues, a fertility specialist can evaluate for LUF and recommend targeted treatments to increase your chances of pregnancy.