For most women, the natural decline of reproductive hormones is what causes menopause. The changes begin in a stage before menopause called perimenopause or climacteric. In this stage, a woman’s supply of mature eggs diminishes. Ovulation becomes irregular. This also causes estrogen and progesterone to decrease.
Other causes of menopause are not related to the natural decline of mature eggs. Premature menopause or primary ovarian insufficiency occurs before the age of 40. Risk factors include the following:
- Exposure to radiation usually through radiation therapy
- Surgery that affects blood supply to the ovaries
- Chromosome problems
Surgical menopause is another cause of menopause. If a woman needs a hysterectomy, oophorectomy (removal of one or both ovaries) or pelvic radiation, surgical menopause can occur.