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