LH is released as part of the female menstrual cycle. Its partner is follicle stimulating hormone (FSH), these two hormones work to achieve ovulation, which is controlled by LH. If fertilization does not take place, then their levels drop and menstruation begins. Progesterone and estrogen play a role in this as well. If fertilization takes place, these two hormones help prepare and support fetal development.
The pineal gland plays a role in this as well, and is influenced by the amount of available full spectrum light. For example: In the springtime, when the days get longer, female birds are more likely to ovulate because the pineal gland allows more LH to be released.