Lutenizing hormone controls egg development. LH helps regulate the menstrual cycle and egg production (ovulation). The level of LH in a woman's body varies with the phase of the menstrual cycle. It increases rapidly just before ovulation occurs, about midway through the cycle (day 14 of a 28-day cycle). This is called an LH surge. Consistently high levels of this hormone in your body can prevent this release, and might also be an indicator of Polycystic Ovary Syndrome.