Natural menopause is due to the age-related decline in ovarian follicles and the accompanying changes in hormones. Early menopause can be caused by surgery, cancer treatments, and other medical conditions.

Menopause refers to the time when your menstrual periods stop permanently. When you’ve reached menopause, you can no longer become pregnant.

Reaching menopause is a natural part of aging for many women. However, in some situations, it may occur earlier than is typical.

If you’ve ever wondered what exactly causes menopause, we’ve got answers. Continue reading below to learn about the causes of natural and early or premature menopause.

For many women, menopause happens naturally as they age. You’ve reached menopause when you haven’t had a menstrual period for 12 months.

According to the National Institute on Aging, most women enter the menopausal transition, also called perimenopause, between the ages of 45 and 55. The average age at which women in the United States reach menopause is 52.

You’re born with thousands of ovarian follicles, which are fluid-filled sacs in your ovaries that contain a single egg. As you age, the number of these follicles naturally decreases.

The decline in ovarian follicles is accompanied by changes in hormones associated with your menstrual cycle. Levels of estrogen, which is predominantly made in the ovarian follicles of premenopausal women, start to drop off.

The effects of these natural changes in your body mean that you’ll eventually no longer ovulate. Your menstrual periods will also stop, and you won’t be able to become pregnant.

For some women, menopause can come earlier. This is often referred to as early or premature menopause.

Early and premature menopause can have the same causes. However, what differentiates them is the age at which they happen.

According to the Office on Women’s Health, early menopause happens prior to age 45, while premature menopause occurs before the age of 40.

While sometimes the cause of early or premature menopause is unknown, there are several factors that can cause it, including:

  • surgery
  • cancer treatment
  • other medical conditions
  • genetics
  • environmental exposures

The following sections describe each of these potential causes of early menopause in more detail.

Surgery

Surgical removal of both ovaries, which doctors call a bilateral oophorectomy, leads to menopause. In fact, one 2023 study found that bilateral oophorectomy was the most common cause of premature menopause in the population studied.

A bilateral oophorectomy is often done at a younger age to treat gynecological cancers like ovarian cancer, cervical cancer, and uterine cancer. It may also be used to reduce your risk of ovarian cancer if you have certain genetic changes like those in the BRCA gene.

Removal of one ovary is called a unilateral oophorectomy. While this won’t cause you to go into menopause, it may contribute to experiencing menopause a little earlier than normal. Noncancer-related reasons for a unilateral oophorectomy can include conditions like ovarian cysts and endometriosis.

Having your uterus removed, called a hysterectomy, can cause your period to stop, but this isn’t the same thing as menopause. A hysterectomy may be done to treat:

If your ovaries are left in place during your hysterectomy, you won’t experience immediate menopause symptoms like you would after a bilateral oophorectomy.

However, like a unilateral oophorectomy, a hysterectomy may contribute to you entering menopause a few years earlier.

Cancer treatment

Some cancer treatments may affect the ovaries and lead to an earlier than normal menopause. According to the American Cancer Society, these treatments include certain types of chemotherapy, radiation therapy, and hormone therapy.

In some situations, menopause due to cancer treatment is temporary. However, in others, it’s permanent. If you’re going to be receiving treatment for cancer, be sure to ask your doctor about what effects it may have on your ovaries.

Other medical conditions

In certain autoimmune diseases, your immune system may also mistakenly attack the ovaries. Hashimoto’s thyroiditis, Grave’s disease, and Addison’s disease are examples of autoimmune diseases that can lead to earlier menopause.

Living with HIV can also be associated with reaching menopause at an earlier age. The exact reason behind this isn’t well understood.

Genetics

Genetics can play a role in when you reach menopause. That means that if other women in your family have experienced early or premature menopause, you may be more likely to as well.

Researchers have found genetic changes that are linked with earlier menopause.

Additionally, medical conditions affecting chromosomes, such as Turner syndrome and fragile X syndrome can also lead to early or premature menopause.

Environmental exposures

Smoking is linked with a risk of early menopause. This relationship is dose-dependent, meaning that the more you smoke, the higher the risk of early menopause.

In addition to cigarette smoke, certain other environmental contaminants can also affect the reproductive system and lead to earlier menopause. Examples include:

Menopause is a natural part of a woman’s life. Most women enter menopause in their early 50’s.

Natural menopause happens due to the decrease in ovarian follicles that happens with age and the accompanying hormone changes, such as a decrease in estrogen.

It’s also possible for menopause to happen earlier. Depending on a woman’s age, this may be called early menopause or premature menopause. Early menopause may be caused by things like surgery, cancer treatment, and other medical conditions.