Luteinizing hormone (LH) is produced by the pituitary gland in the brain. It regulates the menstrual cycle. Throughout most of the menstrual cycle, LH levels remain low. However, mid-cycle, as an egg prepares for release, there is a rapid increase in LH, known as an “LH surge.” This LH surge signals impending ovulation, the process where a mature egg is released from the ovary. After its release, the egg travels down the fallopian tube, where it can be fertilized. The LH surge indicates a woman’s most fertile period.
The Typical Ovulation Process
The follicular phase begins with the growth of fluid-filled sacs in the ovaries, called follicles, each containing an immature egg. As these follicles develop, they produce estrogen, which signals the body that an egg is maturing. When one dominant follicle reaches a certain size, the high estrogen levels trigger the pituitary gland to release a surge of luteinizing hormone.
The LH surge causes the mature follicle to rupture and release the egg, typically within 24 to 36 hours. After the egg is released, the remnants of the follicle transform into a structure called the corpus luteum. The corpus luteum then produces progesterone, a hormone that prepares the uterine lining for a potential pregnancy. If fertilization does not occur, the corpus luteum breaks down, progesterone levels drop, and menstruation begins.
Reasons Ovulation May Not Occur
While an LH surge is a strong indicator of impending ovulation, it does not always guarantee that an egg will be released. Several factors can disrupt this process. In some cases, the body may experience a surge in LH, but ovulation, the actual release of the egg, fails to happen.
Anovulation, where ovulation does not occur, is a common reason. Conditions like Polycystic Ovary Syndrome (PCOS) are frequently associated with anovulation, even when an LH surge is detected. High levels of stress or significant fluctuations in body weight can also interfere with the delicate hormonal balance required for ovulation, leading to an LH surge without subsequent egg release.
Another scenario is Luteinized Unruptured Follicle Syndrome (LUFS), sometimes called “trapped egg syndrome.” In LUFS, the follicle containing the egg matures and produces hormones as it should, but it fails to rupture and release the egg. Despite the LH surge and the hormonal changes that follow, the egg remains trapped within the ovary, making conception impossible.
Some individuals may also experience more than one LH surge within a single cycle. This can occur if the initial surge was not sufficient to trigger ovulation, prompting the body to attempt another release. Around one-third of cycles may show two LH surges, and occasionally more than two surges occur, which is generally considered normal.
However, it can make interpreting at-home LH tests challenging, as multiple positive results might appear without a confirmed ovulation. Furthermore, misinterpreting LH test results can happen due to user error or individual variations in hormone timing. The fertile window is brief, and the timing of the surge relative to actual ovulation can vary.
Confirming Ovulation
Since an LH surge does not definitively confirm ovulation, other methods are available to verify if an egg has been released. Basal Body Temperature (BBT) charting involves tracking the body’s resting temperature each morning. A sustained rise in BBT, typically by 0.4 to 1.0 degrees Fahrenheit, indicates that ovulation has likely occurred, as progesterone causes this elevation.
Progesterone testing is a more direct way to confirm ovulation. After an egg is released, the corpus luteum produces progesterone. A blood test, often performed around day 21 of a 28-day cycle, can measure progesterone levels. A progesterone level above a certain threshold, generally 5 ng/mL, indicates that ovulation has taken place. Urine tests that measure pregnanediol glucuronide (PdG), a metabolite of progesterone, can also be used at home to confirm ovulation.
Ultrasound monitoring offers a visual confirmation of ovulation. Through serial transvaginal ultrasounds, healthcare providers can track the growth of ovarian follicles and observe whether the dominant follicle ruptures to release the egg. This method can directly visualize the process and confirm if ovulation has happened.
When to Seek Professional Guidance
Recognizing when to consult a healthcare professional regarding ovulation is important for reproductive health. If you consistently observe positive LH surges but do not experience other signs of ovulation, such as a sustained rise in basal body temperature or changes in cervical mucus, seeking medical advice is recommended. This pattern might indicate an underlying issue preventing egg release.
Difficulty conceiving after a certain period of trying, despite diligently tracking LH surges and timing intercourse, also warrants professional evaluation. Generally, if you are under 35 and have been trying to conceive for 12 months, or over 35 and have been trying for 6 months, it is advisable to consult a fertility specialist.
Irregular menstrual cycles, or symptoms suggestive of hormonal imbalances like Polycystic Ovary Syndrome (PCOS), are additional reasons to seek guidance. A healthcare provider can conduct further tests to diagnose any conditions affecting ovulation and discuss appropriate treatment options. Ultimately, for any concerns about fertility or menstrual health, professional medical advice provides accurate diagnosis and personalized care.