Postmenopausal osteoporosis

During and after the menopause there is a marked tendency for women to lose bone material. Bone density decreases with time and may cross a hypothetical fracture threshold.

Thereafter the patient is at an increased risk of bone fractures including:

• crush fractures of the vertebral body
• neck of femur
• distal forearm

The time taken to reach the threshold depends on:

• the peak bone mass } factors affecting these are
• the rate of bone loss } discussed under risk factors

In the decade immediately preceding the menopause, there is an annual rate of bone loss of about 0.3% of bone mass per year. This increases to 1-3% in the first 4 years after the menopause but then slows to about 0.6% subsequently.

Postmenopausal osteoporosis is thought to result from osteoclastic activity unbalanced by that of osteoblasts as the latter have been shown to be directly stimulated by oestrogens.