Understanding LH Surges During Perimenopause

During perimenopause, the body undergoes many hormonal changes that can affect how the menstrual cycle works. One important hormone involved in this process is luteinizing hormone, or LH. Understanding what happens with LH during perimenopause can help explain some of the changes and symptoms women experience.

LH plays a key role in triggering ovulation, which is when an egg is released from the ovary. Normally, during a regular menstrual cycle, estrogen levels rise and reach a peak just before mid-cycle. This peak causes a sudden increase in LH levels—called an LH surge—which signals the ovary to release its mature egg. This surge usually happens about 24 to 36 hours before ovulation and is essential for fertility.

However, during perimenopause—the transition period leading up to menopause—hormone levels start fluctuating more unpredictably. Estrogen production becomes irregular and often declines overall. Because estrogen triggers the LH surge, these fluctuations can cause irregular or weaker surges of LH. Sometimes there may be multiple smaller surges instead of one clear big spike.

As a result, ovulation may become less consistent or even stop happening altogether at times during perimenopause. This leads to irregular menstrual cycles—periods might come earlier or later than usual or skip entirely for months at a time.

The changing pattern of LH surges also affects other hormones like progesterone that prepare the uterus for pregnancy after ovulation. When ovulation doesn’t occur regularly due to disrupted LH signaling, progesterone levels drop too low or become erratic. This imbalance contributes not only to irregular periods but also common symptoms such as hot flashes, mood swings, night sweats, and sleep disturbances experienced during perimenopause.

Because detecting an LH surge has been used traditionally by women trying to conceive—to know their most fertile days—it becomes more complicated in perimenopause when these surges are unpredictable or absent.

In summary: The normal mid-cycle spike in luteinizing hormone that triggers egg release becomes less reliable as women enter perimenopause due to fluctuating estrogen levels and ovarian aging. These changes disrupt regular cycles and fertility while contributing to typical menopausal symptoms through complex hormonal shifts around this critical time in life.