POI, formerly known as Premature Ovarian Failure, occurs when a woman’s ovaries stop functioning properly before she turns 40. The ovaries stop producing estrogen and progesterone, thus ceasing the process of egg release, causing a woman’s periods to become irregular and ultimately stop. Occasionally, the ovaries may restart, temporarily producing hormones and releasing eggs. POI is rare, affecting approximately 1 percent of women, and often leads to infertility.