Aging is the chief cause of menopause. Natural menopause is preceded by a period of transition known as perimenopause. This can begin as early as a woman’s early 30s or – in rare cases – as late as a woman’s late 60s. Perimenopause may end in the course of several months, or may unfold over many years. It is important to note that women can still get pregnant during this time period.

This process that leads to menopause usually begins in a woman’s middle to late 30s, when the ovaries’ production of estrogen and progesterone begins to fluctuate. The hormone levels vary even more during a woman’s 40s and may cause irregular menstrual cycles. By a woman’s mid-50s, menstruation cycles typically cease altogether. When this occurs, it is known as menopause. Most women experience menopause between ages 45 and 55, with the average age being between 50 and 51 years.  

Though most women experience menopause naturally as they age, other factors can trigger premature menopause in women. These include:

• Surgical menopause. Also known as induced menopause, it involves an operation to remove the uterus (hysterectomy) and ovaries (oophorectomy). Such surgery is often necessary to treat conditions like gynecologic cancers or endometriosis. The symptoms are likely to appear immediately after surgery, rather than occurring gradually as they do in natural menopause. In addition, symptoms are often more severe after surgical menopause.
  
  In some cases, women will have their uterus removed, but their ovaries will be left in place. Although these women are no longer able to bear children and do not menstruate, they will not experience premature menopause, as their ovaries will continue to produce hormones. Some of these women will experience hot flashes, as the surgery may disrupt the blood supply to the ovaries. In addition, women who have their uterus removed may experience menopause a year or two earlier than expected, and are at higher risk for osteoporosis.
  
  
• Other forms of early menopause, or premature ovarian failure (POF). In addition to surgery, there are several other potential triggers of premature menopause. This is defined as any menopause that occurs before age 40, whether natural or induced. POF may occur because of several factors, including:
  
  
• • Genetics. The age at which a woman enters menopause often corresponds closely with that of her mother. In addition, twin sisters appear to be at higher risk of experiencing early menopause than women who do not have a twin, according to new research.
    
    
  • Cancer treatments. Chemotherapy or radiation to the pelvic area can damage the ovaries, triggering POF. Female survivors of childhood cancer are more likely to experience early menopause than other women.
    
    
  • Smoking. Tobacco use may cause menopause to occur up to two years earlier than normal.
    
    
  • Chromosome defects. For example, women born without a second X chromosome, or born without part of the chromosome have a condition known as Turner syndrome. In this disorder, the ovaries do not form normally, which leads to early menopause.
    
    
  • Autoimmune diseases. The body’s immune system sometimes mistakenly attacks part of the reproductive system, damaging ovaries and preventing them from producing female hormones. Examples of diseases that can cause these symptoms include thyroid disease and rheumatoid arthritis.
    
    
  In addition, a new study that analyzed data from the renowned Framingham Heart Disease Epidemiology Study found that women with certain risk factors for heart disease (e.g., high cholesterol levels, excess weight, high blood pressure) can experience menopause earlier than women without such risk factors. Premature menopause increases the risk for osteoporosis later in life. Some women may also experience emotional trauma, as POF severely restricts a woman’s ability to have children. Women who still desire to become pregnant should talk to their physician about donor egg programs.