Luteinizing Hormone (LH) is a protein hormone produced by the pituitary gland that plays a precise function in the reproductive cycle. Its primary role is to signal the ovary to release a mature egg, an event known as ovulation. As a follicle develops, it produces increasing amounts of estrogen. Once estrogen reaches a certain threshold, it triggers a dramatic, acute spike in LH release, known as the LH surge. This surge is the direct hormonal signal that triggers ovulation approximately 24 to 36 hours later. People trying to conceive often track this surge using at-home tests to identify their most fertile window. When the expected LH surge fails to appear, it suggests the body has not received the necessary signal to ovulate.
Tracking and Testing Issues
A frequent reason for an absent surge is not physiological failure but a failure to accurately capture the transient hormonal event. The LH surge is often brief, lasting only 12 to 27 hours before hormone levels begin to drop again. If testing is conducted only once a day, especially in the morning, it is easy to miss the peak if the surge occurs between tests.
Testing frequency is a major factor, especially for women with shorter cycles or rapid-onset surges. These individuals may need to test twice daily, perhaps in the mid-morning and early evening, to ensure capture. Furthermore, fluid intake significantly affects the concentration of LH in urine. Drinking large volumes of water shortly before testing dilutes the urine, potentially lowering the LH concentration below the detection threshold of the at-home test kit, resulting in a false negative.
Different ovulation predictor kits (OPKs) possess varying degrees of sensitivity to the hormone, measured in mIU/mL. Some kits have a higher threshold for a positive result. This means a person with a naturally lower, yet still ovulatory, surge might continually see a negative result. A positive result is typically defined when the test line is as dark as or darker than the control line; a faint line does not count as a true surge. Consistently low or negative results may also occur if a person’s baseline LH level is already high, making the final surge too subtle for the test to distinguish from the background level.
Underlying Medical Conditions Preventing Ovulation
When testing issues are ruled out, a persistent absence of the LH surge points toward true anovulation, meaning the hormonal signaling cascade leading to egg release is broken. Polycystic Ovary Syndrome (PCOS) is the most common cause of anovulation. In PCOS, the hypothalamus releases Gonadotropin-Releasing Hormone (GnRH) at a higher frequency than normal, favoring the production of LH over Follicle-Stimulating Hormone (FSH) in the pituitary gland.
This results in a chronically elevated LH level, stimulating the ovaries to produce excess androgens. The sustained high LH, combined with low FSH, prevents the proper maturation of a single dominant follicle. Consequently, the required high estrogen pulse needed to trigger the final LH surge does not occur. The body may attempt to surge repeatedly, resulting in multiple “false” surges or a chronically high baseline that masks a true peak.
Functional Hypothalamic Amenorrhea (HA) is another significant cause, characterized by a “shut down” of the reproductive axis due to chronic energy deficiency or stress. The hypothalamus reduces the pulsatile release of GnRH, causing the pituitary to release insufficient amounts of LH and FSH. This suppression means a follicle never matures enough to produce the estrogen spike needed to initiate the surge. This results in low LH levels and a complete lack of ovulation.
A separate group of conditions involves issues with the pituitary or the ovaries themselves. Hyperprolactinemia, characterized by high levels of prolactin, can directly interfere with GnRH secretion. This leads to an inhibitory effect on LH release and subsequent anovulation. Primary Ovarian Insufficiency (POI), or premature menopause, involves the depletion or malfunction of ovarian follicles. Although POI is characterized by high FSH and LH, the remaining follicles may not produce enough estrogen to trigger the surge, leading to an absence of functional ovulation.
External and Lifestyle Influences
Several external and lifestyle factors can temporarily or chronically disrupt the delicate Hypothalamic-Pituitary-Ovarian (HPO) axis, suppressing the LH surge. Significant or rapid weight fluctuations, both gain or loss, can signal to the brain that energy reserves are unstable. This leads to a disruption in GnRH pulsatility and subsequent failure of the LH surge. Intense or excessive exercise, especially when combined with insufficient caloric intake, can mimic the energy deficiency seen in Hypothalamic Amenorrhea, temporarily suppressing reproductive hormones.
High levels of psychological or physical stress elevate cortisol, which interferes with the signaling pathway controlling GnRH release. This often delays or inhibits the LH surge for that cycle, potentially causing cycles to be anovulatory or erratic. For individuals who recently stopped hormonal birth control, post-pill amenorrhea can occur. In this condition, the HPO axis takes several months to resume its natural cycling after being suppressed by exogenous hormones.
Certain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, may interfere with the release mechanism when taken regularly around ovulation. These drugs inhibit the production of prostaglandins, which are necessary for the follicle wall to break open and release the egg. Although the LH surge itself may still occur and be detected, the final step of follicular rupture is inhibited. This results in an anovulatory cycle where the egg is not released.
Next Steps and Medical Consultation
If a single cycle lacks a detectable LH surge, the first step is to re-evaluate testing technique and continue tracking. However, a pattern of consistently absent surges over two or three cycles warrants professional evaluation. Medical consultation is especially important if you have irregular cycles, no period at all (amenorrhea), or are over the age of 35.
A healthcare provider will likely order a panel of blood tests to assess hormonal status and rule out underlying conditions.
Hormonal Testing
These tests typically include a Day 3 measurement of Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), and Estradiol (E2). These measurements help gauge ovarian reserve and pituitary function. Additional blood work will check Prolactin and Thyroid-Stimulating Hormone (TSH) levels, as imbalances in these hormones can directly inhibit ovulation.
The Anti-Müllerian Hormone (AMH) test, which can be drawn at any point, is valuable for estimating the remaining egg supply. It is recommended to seek a fertility specialist’s evaluation if you are under 35 and have been trying to conceive for 12 months without success. Evaluation is also recommended if you are over 35 and have been trying for six months. For those with consistently absent periods, seeking evaluation sooner is necessary to address the underlying cause of anovulation.