Luteinizing Hormone (LH) is a reproductive hormone produced by the pituitary gland, a small organ located at the base of the brain. This hormone plays a direct role in regulating the ovarian cycle and stimulating the final maturation of the egg. Throughout the menstrual cycle, LH levels fluctuate, but a dramatic increase is the signal the body uses to initiate the release of a mature egg. People who are tracking their fertility use at-home Ovulation Predictor Kits (OPKs) to detect this hormonal shift in their urine. Understanding the patterns of this hormone is necessary for accurately identifying the most fertile days, which can be a confusing task when the LH pattern does not follow the expected single rise.
The Standard Ovulation Trigger
The process that leads to the successful release of an egg, known as ovulation, is initiated by a well-timed sequence of hormonal events. Rising levels of estrogen, secreted by the dominant ovarian follicle, signal the brain that an egg is ready for release. When the estrogen concentration reaches a high enough threshold, it triggers a positive feedback loop within the hypothalamic-pituitary-ovarian axis.
This signal causes the pituitary gland to release a large, acute quantity of Luteinizing Hormone, which is referred to as the LH surge. This surge is the biological trigger that compels the dominant follicle to rupture and release the egg. Ovulation reliably occurs approximately 24 to 36 hours after the surge begins, or about 10 to 12 hours after the hormone reaches its peak concentration. After the egg is released, the LH levels quickly drop back down to their baseline, marking the start of the post-ovulatory phase.
Explaining the Premature LH Rise and Fall
It is common for the body to show an initial rise in LH that then falls back to baseline levels without being followed by ovulation. This phenomenon is often termed a “failed surge” or “false surge” because the hormonal signal was insufficient to complete the biological task. The initial rise indicates the body was attempting to ovulate, but the LH signal was not sustained at the necessary concentration or duration to trigger the follicle rupture.
Following a failed attempt, the body often produces a “second surge,” or multiple waves of LH within the same cycle, as it tries again to mature and release the egg. Studies have shown that this pattern, sometimes called a double LH surge, may occur in a significant number of cycles. In these cases, the second, more robust surge is typically the one that is successful in triggering the release of the egg. The initial rise and fall may simply reflect the body testing the waters before committing to the full hormonal spike.
Hormonal and Biological Reasons for Fluctuation
The occurrence of premature or insufficient LH surges is a symptom of a disruption in the precise hormonal communication necessary for healthy ovulation. The most immediate outcome of a failed surge is an anovulatory cycle, where the egg is not released at all despite the body’s efforts. The delicate balance between estrogen and LH is easily disturbed by underlying conditions that lead to these erratic patterns.
Polycystic Ovary Syndrome (PCOS) is a frequent cause of LH fluctuation, as the condition often involves chronically high or erratic baseline LH levels. These elevated hormone levels can make it difficult for the body to produce the clean, sharp surge needed for ovulation, leading to multiple smaller peaks that do not fully trigger the process.
Factors like significant emotional or physical stress can also interfere, as high levels of the stress hormone cortisol can suppress the release of Gonadotropin-Releasing Hormone (GnRH), which is upstream of LH. Additionally, conditions such as thyroid disorders, high prolactin, or the natural hormonal shifts of perimenopause may also contribute to irregular LH signaling.
Improving Accuracy in LH Testing and Interpretation
When tracking LH levels, especially when fluctuations are observed, the timing and technique of testing are crucial for accurate interpretation. The Luteinizing Hormone is synthesized by the body in the morning, but it takes time to appear in the urine, making first morning urine samples less ideal for detection. Testing consistently in the afternoon or early evening is generally advised to catch the hormone at its peak concentration in the urine.
If an initial rise and fall is detected, testing twice a day—once in the late morning and again in the early evening—may be necessary to ensure a potentially short, successful surge is not missed. Limiting fluid intake for two hours before testing can prevent urine dilution, which causes a false negative result.
Ovulation Predictor Kits only predict the potential for ovulation; they do not confirm that the egg was actually released. To confirm ovulation occurred, tracking the slight rise in Basal Body Temperature (BBT) after the LH surge is often used as a complementary method.