Structural problems. Abnormalities in the structure
of the ovaries (such as
ovarian cysts) or structural problems in other
reproductive organs can cause changes in a woman's ovulation schedule.
General medical problems. Medical problems that
metabolism (such as
thyroid problems), serious illness, emotional stress,
overweight and low weight, or excessive exercise can affect a woman's ovulation
Cancer treatment. Exposure to certain kinds of
chemotherapy or radiation can damage the egg supply in the ovaries.