And those led to the modern understanding that many corals reproduce only once or twice a year, in coordinated mass releases of eggs and sperm. (sciencenewsforstudents.org)
For example, at ovulation, usually around Day 12 — 14 of a woman's menstrual cycle, increased estrogen levels trigger a sharp rise in Luteinizing Hormone (LH) from the pituitary gland, causing release of the egg from the follicle. (vitalise.ie)
Birth control pills contain hormones to prevent ovulation (release of an egg for possible fertilization), so the uterine lining doesn't really develop. (blog.advocatesaz.org)