Définition
The LH surge is a sharp rise in luteinizing hormone that triggers ovulation approximately 24–36 hours later. It is the cycle's most precise timing signal — detectable with ovulation predictor kits — and marks the transition from follicular to luteal phase physiology.
The LH surge is one of the more elegant feedback loops in human physiology. As estradiol rises during the late follicular phase, it eventually reaches a threshold that flips feedback from negative to positive at the hypothalamic-pituitary axis — producing a sharp increase in GnRH pulsatility and a corresponding surge in luteinizing hormone (LH) from the pituitary. LH reaches 3–8x baseline levels over 24–36 hours.
The biological consequence is ovulation: the mature follicle ruptures, releasing the oocyte. The remnant follicular tissue then becomes the corpus luteum, which begins producing progesterone. This transition from LH surge → ovulation → corpus luteum formation takes approximately 24–48 hours and marks the physiological crossover from follicular to luteal phase.
The LH surge is detectable non-invasively through urine-based ovulation predictor kits (OPKs), which measure LH concentration in urine. A positive test typically indicates that ovulation will occur within 12–36 hours. Digital fertility monitors (like the Mira system) provide quantitative LH tracking rather than just threshold detection, which helps women with irregular cycles.
For women tracking their cycles — for fertility, for training periodization, or simply to understand their own patterns — the LH surge is often the most useful single data point. It reliably identifies the cycle's turning point. Combined with basal body temperature tracking (which confirms ovulation has occurred by detecting the post-ovulatory temperature rise), it provides a reasonably accurate window of the cycle phase.
The LH surge is affected by several factors that women with irregular cycles encounter: chronic stress (elevated cortisol blunts GnRH pulsatility), low energy availability (RED-S), very low body fat, thyroid dysfunction, and PCOS (where LH is often chronically elevated rather than pulsatile). Consistent surge detection month to month is a marker of reproductive health even independent of pregnancy intent.
Termes associés
Ava Longevity · Built on the Ava Method · MMXXV