Consequences of oestrogen deficiency after menopause on bone health

Menopause refers to the time in a woman’s life when she ceases to menstruate. In Australia the average age of menopause is approximately 51 years. However, it can occur from any time between 45 and 55 years of age.

Menopause is a natural part of life. Menopause can also occur after surgical removal of the ovaries or after chemotherapy, particularly in the setting of treating breast cancer. This is referred to as iatrogenic (medically caused) menopause. Menopause represents the time when the ovaries cease to function and thereby no longer produce eggs (ova) or the usual hormones that support the normal menstrual cycle: oestrogen and progestin. Thus menopause results in oestrogen deficiency.

It is also known that oestrogen levels begin to fall in the years preceding menopause, even when a woman continues to menstruate normally. It is this oestrogen deficiency around the time of menopause that contributes significantly to bone loss in women.

Irrespective of the cause of menopause, the resultant oestrogen deficiency has significant effects on bone health.

Prior to the menopause, there is almost no bone loss occurring and the likelihood of fractures is low. In the immediate years following menopause, there is a rapid phase of bone loss, which can last from four to eight years.⁴ Usually, the majority of bone is loss occurs in the first 3 years after menopause and then the rate of bone loss slows.⁵ During the first 3 years after menopause, women may lose up to approximately two per cent of bone mass per year especially in the spinal bones (vertebral bones). ^5,31,32 The extent of bone loss in hips and wrist may be similar or slightly less.^5,31,32 This rapid loss of bone results in an increased risk of fracture particularly at the spine and forearm.

Once the rapid phase of bone loss subsides, women then undergo a slow phase of bone loss, which continues indefinitely. This phase of bone loss is part of normal ageing and affects both men and women. During this phase, women can expect to lose one per cent of bone mass from the hips per year and just less than one per cent of bone mass from the spine.^5,31,32

Oestrogen deficiency leads to an imbalance favouring bone breakdown over bone formation. It also causes a negative balance of body calcium by reducing the ability of the gut and kidney to maintain adequate calcium levels. These factors all combine to reduce bone strength after the menopause. Apart from losing bone mass, structural changes occur within bone such as increased number of perforations (holes in bone surfaces) and reduced bone connectivity (which leads to reduced bone strength). Importantly, women who have achieved low peak bone mass or who have reduced bone mass for other reasons will be at increased risk of osteoporosis.

Maintaining bone health

Activity and lifestyle

Management of bone health after menopause involves attention to lifestyle factors.

Regular exercise, adequate dietary calcium intake and trying to optimise vitamin D levels are simple ways to prevent osteoporosis. As a rough guide, postmenopausal women need three to four serves of dairy products daily. Women who are unable to consume this quantity of dairy products daily may need calcium supplements.

For more information go to Prevention

Hormone therapy

Hormone therapy after the menopause leads to increased bone density and reduction in fractures. The Women’s Health Initiative Trial (WHI, published July 2002 and October 2003)  showed that hormone therapy was highly effective in reducing the incidence of fractures in postmenopausal women.^36,37,88

However, long-term hormone therapy was associated with a risk of heart disease, breast cancer, pulmonary embolism (blood clots in the lung) and deep vein thrombosis (blood clots in the leg veins) in the WHI study. Hence, although hormone therapy has beneficial effects on bone health, it should be prescribed primarily for short-term treatment (less than five years) of menopausal symptoms in women who are progressing through menopause.

The use of hormone therapy for treatment of osteoporosis is not currently recommended as first line therapy in post-menopausal women.

It is also important to realise that the beneficial effects of hormone therapy on bone last only whilst the woman is on treatment. When therapy is ceased, the rate of bone loss returns to the rate at which it was progressing before the therapy started.³⁹

Bone health assessment

Postmenopausal women who are concerned about their bone health should see their doctor and have an assessment for osteoporosis (bone density measurement).

If osteoporosis is found in a bone density study the options for treatment include exercise, increasing dietary calcium intake, optimising vitamin D levels and some specific osteoporosis medications.

Your doctor may recommend other therapies more specific to the treatment of osteoporosis, based on your current overall risk of fracture. The risk of fracture increases if you have:

• a previous fracture
• a family history of fractures
• a history of (or current) smoking or excessive alcohol consumption
• received corticosteroid treatment

If you are found to have had an osteoporosis related fracture (low trauma fracture), your doctor is likely to prescribe specific drug therapy for osteoporosis.

Content updated July 29, 2011