Cessation of menstruation can be caused by excessive caloric restriction, caloric deficit from excessive physical activity, or lifestyle factors affecting the hypothalamus or pituitary.

“Keeping in mind, of course, that if your total number of calories is too low, your periods will cease. That's a well-known effect. But of course, stress can also induce cessation of menstruation. And there are other factors that can induce cessation of menstruation as well. Some of them start with changes in the brain, literally, in the hypothalamus. Some occur in the pituitary. Many lifestyle factors can do that. But most typically, it's going to be excessive caloric restriction or it's going to be a caloric deficit brought on by excess physical activity.”