1.   Men who do not produce any estrogen keep growing.

2.   The theory is that women produce melatonin at night, and when melatonin is low the body produces more estrogen, which poses a cancer risk.

3.   Biologists have long known that estrogen is produced not only in the ovaries but also in fat cells.

4.   Cancer treatment often makes young women infertile, stopping the ovaries from producing estrogen and bringing on early menopause.

5.   Fat cells produce estrogen, and many believe the extra hormone is what puts overweight women at higher risk of breast cancer.

6.   Female sex organs, which produce estrogen, are inactive until later.

7.   It usually develops after menopause when natural estrogen, a protective hormone, is no longer produced.