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 – 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.
In the immediate years following menopause, there is a rapid phase of bone loss, which can last from 4 – 8 years.4 Usually, however, most bone is lost 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 2% 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
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 not only affects women but also men. During this phase women can expect to lose 1% of bone mass from the hips per year and just less than 1% of bone mass from the spine.5,31,32
Oestrogen deficiency also results in impaired gut (gastrointestinal system) absorption of calcium from the diet. The kidney also becomes less efficient in conserving calcium.4 As a result, there is a relative decline in available calcium in the blood. The body works at all costs to try and maintain the normal levels of calcium in the blood. As the human skeleton is the major storage organ for calcium, the body compensates for the relative decrease in available calcium from the gut and kidney by leaching calcium out of the bones.4 Thus not only do the bones become weaker because of oestrogen deficiency at menopause, they also lose more calcium. Therefore, the way to reduce the loss of calcium from the bones is to increase the intake of calcium from the diet or to take calcium supplements.
Maintaining Bone Health
Activity and Lifestyle
Management of bone health after menopause involves attention to lifestyle factors.
Prevention
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 3 to 4 serves of dairy products daily. Women who are unable to consume this quantity of dairy products daily, may need calcium supplements.
Hormone Therapy
Hormone therapy at the time of menopause may also be beneficial for protecting bones. The Women’s Health Initiative Trial (published July 2002 and October 2003) has shown that hormone therapy does reduce the incidence of fractures in postmenopausal women.36,37,88
However, long-term hormone therapy is associated with other risks of heart disease, breast cancer, pulmonary embolism (blood clots in the lung) and deep vein thrombosis (blood clots in the leg veins). Hence, although hormone therapy has beneficial effects on bone health, it should be prescribed primarily for the short-term treatment (less than 5 years) of menopausal symptoms in women who are progressing through menopause.
The use of hormone therapy for disease prevention is not recommended.
It is also important to realise that the beneficial effects of hormone therapy only last whilst the woman is on treatment. When hormone therapy is ceased the rate of bone loss returns to the level it would been had the woman not been on hormone therapy.39
Bone Health Assessment
Postmenopausal women who are concerned about their bone health need to see their doctor and have an assessment for osteoporosis.
If osteoporosis is found, based on the findings of a bone DEXA study, the options for treatment include exercise, increasing dietary calcium intake and optimising vitamin D levels.
Your doctor may recommend other therapies more specific to the treatment of osteoporosis, especially if there are other significant risk factors for osteoporosis present, such as chronic corticosteroid therapy.
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 27, 2009
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