2.2.3 What causes osteoporosis?
Many factors contribute to the development of osteoporosis. Loss of bone mass starts to occur after the age of 30. Peak bone mass, which is reached in young adulthood, is set by three main factors:
- genetics (which accounts for 70-80% of the variation in peak bone mass)
- diet and lifestyle
- exercise levels
Load bearing exercise also encourages the osteoblasts to form more bone tissue.
The speed of bone loss is influenced by diet, disease and absorption of vitamin D (discussed in 4.2.2). An adequate diet supports the maintenance of a healthy bone matrix and stops the body needing to draw on the calcium reserves in the skeleton. Lifestyle factors including both alcohol and tobacco use lead to lower bone mineral density. Hormones also play a role in this. For example, in women, after the menopause, there is a period of accelerated bone mineral density loss due to the reduction in oestrogen levels. Anti-hormone cancer treatments, such as for prostate or breast cancer, suppress sex hormones and discourage bone formation. Different illnesses speed up bone loss. Many medications can reduce bone density, perhaps, most importantly, steroids and anti-epileptics. Lastly, even without measured low bone mass or density, conditions that cause high bone turnover reduce the structural integrity of bone – particularly of trabecular bone.
2.2.2 Osteoporosis and fragility fractures