Progesterone plays a critical role in balancing estrogen’s effects on the uterine lining. In a normal menstrual cycle: Estrogen builds up the uterine lining (called the proliferative endometrium). Progesterone comes in after ovulation and stabilizes and matures that lining, converting it into a secretory endometrium—a plush, nutrient-rich environment ready for a fertilized egg to implant.

There are two types of estrogen therapy, local estrogen therapy and systemic estrogen therapy.

If you’ve managed to make it through most of your adult years with regular, “normal” periods but now suddenly find yourself with heavy or irregular bleeding, it can be rather alarming.