Bone cells are constantly dying and being renewed, but in patients with osteoporosis not enough new bone forms. This means they become more porous, weaker and more prone to fracturing. The condition often goes undetected and can cause no symptoms – until bones break.
Broken hips, wrists and spinal vertebrae are common in people with the condition.
Over time, some people who suffer spinal fractures may also develop a stooped posture, as the spine struggles to support the weight of their body, and this can lead to breathing difficulties.
Osteoporosis is more common in women than men – particularly after the menopause – because of falling levels of the female sex hormone oestrogen, which is vital for healthy bone formation.
Patients with osteoporosis have two main types of drug treatment available. The first slows the rate of bone loss, while the second encourages new bone to form.
For almost a decade, no new drugs were deemed effective or safe enough to be given to patients.
But at the end of 2019, the European Medicines Agency approved romosozumab, a new type of bone-forming treatment.
The new treatment, which has the brand name Evenity, works by blocking sclerostin, a substance that stops new bone cells forming.
A study found that post-menopausal women with osteoporosis who were given the new drug had a 73 per cent lower chance of developing a new spinal fracture after a year, compared with women who received a placebo.
The treatment has also been shown to increase the density of the thigh bone, hip and vertebrae.
However, it is not suitable for everyone. Osteoporosis patients at a high risk of a heart attack or stroke should not be given the drug, as one study found it could increase the chances of either happening.
While the drug is being trialed in countries like the UK, it has yet to become widely available in the developing world, leaving many suffers without access to medical care that could improve their condition.