Women may lose their periods as a result of pregnancy. No other eggs are released during pregnancy, so menses does not occur. Women also naturally lose their periods at menopause, as a result of hormonal changes. Starvation diets and some medications can also cause menses to cease. Some birth control medications also prolong the delay between cycles.
There are lots of reasons this can occur. There is disorder (PCOS, etc), being overweight, being underweight, eating disorders, malnutrition, operations, and simple stress or change on the body are all causes.
There are two major causes of period loss in Women. Reason one is due to pregnancy, which causes the period to stop until after the baby is born. The second major reason is stress. It could be stress at home or work and even can occur from a major change in your life such as a new job or moving.