Women begin to go through menopause around the age of 40, according to WebMD. Premature menopause is considered menopause before the age of 40 regardless if it is from natural causes or the result of surgery.
The number of eggs stored in the ovaries is finite. Once all the eggs are released, hormonal levels of estrogen and progesterone begin to decline signaling the body to start the menopause process. This causes the menstrual cycle to stop. Natural menopause has three stages, and it is gradual. It consists of perimenopause, which starts about one to two years before menopause. Then, the menopause stage, which leads into the postmenopause stage where symptoms generally ease up but lead to health risks associated with the loss of estrogen, explains WebMD.