Osteoporosis Causes in Women: Why Women Lose Bone and Who Is Most at Risk

Women are more likely than men to develop osteoporosis, particularly after menopause. But osteoporosis in women does not have one single cause. Bone strength is influenced throughout life by:

• How much bone a woman builds during childhood and early adulthood
• Hormone levels
• Age and menopause
• Nutrition
• Physical activity
• Family history
• Medical conditions
• Medicines that affect bone

For some women, osteoporosis mainly develops because of ageing and the fall in estrogen after menopause. For others, another condition—such as early menopause, long-term steroid treatment, an eating disorder, thyroid disease, malabsorption or certain cancer treatments—accelerates bone loss. Understanding the cause matters because it can influence both fracture risk and treatment.

For a broader overview of diagnosis and treatment, see our main guide to Osteoporosis Treatment.

Why Is Osteoporosis More Common in Women?

There are two major biological reasons. First, women generally have smaller bones and lower peak bone mass than men. Second, estrogen plays an important role in protecting bone. When estrogen levels fall sharply around menopause, bone breakdown increases and women can begin losing bone more quickly.

This does not mean menopause automatically causes osteoporosis. A woman's eventual risk depends on both:

• How strong her bones were before menopause
• How quickly she loses bone afterward

How Does Bone Loss Develop in Women?

Bone is living tissue. Throughout life, old bone is continuously removed and replaced with new bone. This process is known as bone remodeling. During childhood, adolescence and early adulthood, bone formation generally exceeds bone loss, allowing the skeleton to become stronger.

Later in life, the balance begins to shift. When more bone is broken down than rebuilt over a long period, bone density and bone strength decline. Eventually, this can lead to osteoporosis and an increased risk of fractures.

The Causes of Osteoporosis Can Change Across a Woman's Life

1. Menopause and Falling Estrogen

Menopause is one of the most important causes of accelerated bone loss in women. Estrogen normally helps limit the rate at which old bone is broken down.

As estrogen falls around menopause, bone resorption increases. For many women, the years immediately around and after menopause are therefore a period of relatively rapid bone loss. The effect is particularly important if a woman already has:

• Low bone density
• Low body weight
• A family history of osteoporosis
• A previous fragility fracture
• Other medical or medication-related risk factors

2. Early Menopause

The earlier estrogen levels fall, the longer a woman's bones may be exposed to low estrogen. This is why early menopause increases osteoporosis risk.

Risk may be greater in women who experience menopause before approximately age 45, particularly when menopause occurs much earlier than expected. Premature ovarian insufficiency, in which the ovaries stop functioning normally before age 40, also deserves careful attention to long-term bone health.

3. Removal of the Ovaries

Surgical removal of both ovaries before natural menopause can cause a sudden fall in estrogen. This is known as surgical menopause. 

Because the hormonal change happens abruptly, bone loss may accelerate if appropriate preventive measures are not considered. It is important to distinguish this from hysterectomy alone.

Removing the uterus does not necessarily cause the same sudden estrogen loss if the ovaries remain functioning. The bone-health concern is particularly important when the ovaries are also removed or ovarian function is lost prematurely.

4. Absent or Irregular Menstrual Periods

Osteoporosis can also develop in younger women when estrogen remains low for a prolonged period. One warning sign is amenorrhea—the absence of menstrual periods. This may occur because of:

• Very low body weight
• Eating disorders
• Excessive energy expenditure from intense exercise
• Certain hormonal disorders
• Chronic illness

5. Not Building Enough Bone Earlier in Life

Osteoporosis is not caused only by bone loss later in life. Some women begin adulthood with a lower amount of bone than others. Peak bone mass is influenced by:

• Genetics
• Childhood and teenage nutrition
• Calcium and vitamin D intake
• Physical activity
• Hormonal health
• Long-term illness during growth

6. Ageing

Menopause and ageing are related but not identical causes of bone loss. Even after the faster postmenopausal period slows, bone loss continues with advancing age. Older women may also:

• Form new bone less efficiently
• Lose muscle strength
• Become less physically active
• Absorb nutrients less effectively
• Develop more medical conditions
• Take more medicines that affect bone or balance

7. Family History and Genetics

Bone density and fracture risk have a strong genetic component. A woman's risk is higher if a parent has:

• Osteoporosis
• A history of hip fracture
• Marked age-related height loss or fragility fractures

Genetics can influence peak bone mass, bone structure, hormone regulation and other characteristics affecting fracture risk. You cannot change your family history, but knowing about it can help identify the need for earlier assessment.

8. Low Body Weight and Being Very Thin

Women with low body weight or a small body frame may have less bone reserve. Very low weight can become especially harmful when it is accompanied by:

• Insufficient calorie intake
• Low protein intake
• Vitamin or mineral deficiency
• Loss of menstrual periods

9. Thyroid Disease

Excess thyroid hormone can increase bone turnover and contribute to bone loss. This may occur with:

• Untreated hyperthyroidism
• In some cases, excessive thyroid hormone replacement

10. Hyperparathyroidism

The parathyroid glands help regulate calcium levels in the blood. In primary hyperparathyroidism, excess parathyroid hormone can increase the release of calcium from bone and reduce bone density. Because this is a potentially treatable secondary cause, doctors may check calcium and parathyroid hormone levels when investigating unexplained osteoporosis.

11. Calcium and Vitamin D Deficiency

Calcium is an essential structural component of bone, while vitamin D helps the body absorb calcium and supports normal bone mineralisation. Long-term inadequate intake or deficiency can contribute to poor skeletal health. Risk may be increased in women who:

• Have a very restricted diet
• Avoid major calcium-containing foods without suitable alternatives
• Have vitamin D deficiency
• Have malabsorption
• Spend very little time outdoors

12. Physical Inactivity

Bones respond to mechanical loading. Regular weight-bearing and resistance activities help maintain bone and muscle strength. Prolonged inactivity can contribute to bone loss, particularly when a woman is:

• Bedbound
• Recovering from prolonged illness
• Very sedentary

Does Pregnancy Cause Osteoporosis?

Usually, no. Pregnancy increases calcium demand, especially later in pregnancy, and some calcium is temporarily mobilised from the mother's skeleton. Bone density may therefore decrease somewhat during pregnancy.

For most women, this is a normal and temporary physiological change rather than osteoporosis. Pregnancy-associated osteoporosis is rare. When it occurs, fractures—especially spinal fractures—may develop during late pregnancy or shortly after delivery.

Why Osteoporosis in a Young Woman Needs a Different Approach

Osteoporosis is much less common before menopause. When a younger woman develops unusually low bone density or a fragility fracture, doctors often look carefully for a secondary cause. Possible explanations include:

• Eating disorders
• Prolonged amenorrhea
• Premature ovarian insufficiency
• Glucocorticoid treatment
• Coeliac disease or malabsorption
• Endocrine disease
• Chronic inflammatory illness
• Certain medications

What Causes Osteoporosis After Menopause?

Postmenopausal osteoporosis usually results from several factors acting together rather than estrogen loss alone. These may include:

• Falling estrogen
• Increasing age
• Lower peak bone mass
• Genetic risk
• Reduced activity
• Low body weight
• Vitamin D deficiency
• Medications
• Chronic medical conditions

Which Women Should Be Particularly Alert to Osteoporosis Risk?

Bone-health assessment is especially worth discussing if you:

• Have already had a fragility fracture
• Went through menopause unusually early
• Had both ovaries removed before natural menopause
• Have been without menstrual periods for a prolonged period for reasons other than pregnancy
• Take long-term glucocorticoid medication
• Take an aromatase inhibitor for breast cancer
• Have coeliac disease or another malabsorption condition
• Have rheumatoid arthritis
• Have hyperthyroidism or hyperparathyroidism
• Have very low body weight
• Have a parent with a history of hip fracture
• Smoke or consume alcohol heavily

The Bottom Line

The most common causes of osteoporosis in women are ageing and the loss of estrogen around menopause, but they are far from the only causes.

A woman's osteoporosis risk begins to develop long before menopause because the amount of bone she builds during adolescence and early adulthood determines how much bone reserve she has later. After menopause, falling estrogen accelerates bone loss. Early menopause, premature ovarian insufficiency and removal of both ovaries can expose the skeleton to low estrogen earlier and therefore increase risk.

In younger women, osteoporosis is less common and should raise particular attention to secondary causes such as eating disorders, prolonged amenorrhea, hormonal disease, malabsorption, long-term steroid therapy or chronic illness. Some breast cancer treatments, especially aromatase inhibitors and ovarian-suppression therapy, can also accelerate bone loss.

Pregnancy and breastfeeding deserve a different interpretation: temporary decreases in bone density can occur normally, but bone generally recovers afterward, and pregnancy- or lactation-associated osteoporosis is rare.

Most importantly: Osteoporosis in women is rarely explained by one factor alone. Understanding when bone loss began—and whether menopause, hormones, medicines, nutrition or another disease is contributing—helps doctors identify women at risk earlier and choose the most appropriate way to protect their bones.