Endurance exercises such as running or swimming can affect the reproductive physiology of female athletes.

A more recent study shows that athletes competing in sports that emphasise thinness or a specific weight exhibit a higher rate of menstrual dysfunction than either athletes competing in sports with less focus on these or control subjects.

[6] Breastfeeding has been linked to irregularity of menstrual cycles due to hormones that delay ovulation.

PCOS is a condition in which excessive androgens (male sex hormones) are released by the ovaries.

There is some controversy regarding the mechanism for the menstrual dysregulation, since amenorrhea may sometimes precede substantial weight loss in some anorexics.