Research updates
Osteoporosis   p 13
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6 How is osteoporosis treated? Link to the Medical Research Council web site
6.1 Treatment
There are two types of treatment strategy. The first is population-based, which means that the aim is to make everyone have better bones. The other approach is to target people at highest risk. At present the major thrust in the UK is directed towards the second strategy; the aim is to identify and treat high risk individuals.

Ca2+/vitamin D
Clinical trials of vitamin D plus calcium supplementation have shown a reduction in the risk of hip fracture. It is unclear at present whether the observed benefits are due to vitamin D, calcium or a combination of both.

Trials, organised by the MRC Unit in Southampton, are under way to investigate whether an injection of vitamin D, given annually, reduces the incidence of hip fracture in elderly people. If vitamin D is found to reduce hip fractures it would be a cost-effective way of protecting all elderly people. It would also improve muscle strength and therefore reduce risk of falling.

Hormone replacement therapy (HRT)
For women, HRT is a common means of preventing bone loss after the menopause. The treatment replaces oestrogen. However, the benefit to bone is likely to be lost if HRT is stopped and another complication of HRT, which is difficult to assess, is the increased risk of breast cancer. It is thought that long term use may be associated with a small increased risk.
Selective oestrogen receptor modulators (SERMs)
SERMs mimic the action of oestrogens on certain organs or tissues while simultaneously blocking the effects of oestrogen in others areas. It is hoped that they will reproduce the beneficial effects of oestrogen in protecting against osteoporosis and heart disease, whilst avoiding the increased risk of breast cancer associated with long-term use of HRTs.

Raloxifene is a SERM licensed for women with low spinal density, to reduce risk of vertebral fracture.

Biphosphonates
Biphosphonates are non-hormonal drugs that work by slowing down the cells which break down bone (osteoclasts), enabling the bone building cells (osteoblasts) to work more effectively.

Three biphosphonates are currently licensed for the treatment of osteoporosis. They are:

  • cyclic etidronate
  • alendronate
  • risedronate.
Calcitonin

Calcitonin is a hormone produced by the thyroid gland, which stops the cells that break down bone (osteoclasts) from working properly, allowing the osteoblast cells to build bone more effectively. Calcitonin is not often prescribed as it can only be given by injection. Forms of calcitonin which can be given as a nasal spray or as tablets are being trialled and may be available soon.

6.2 The future
Research may lead to the introduction of strategies to identify and treat those individuals, while they are still children, who are likely to develop osteoporosis in later life.

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Question 12
A new medicine for treating osteoporosis has recently been put forward. This is parathyroid hormone (PTH) delivered by a once daily injection. PTH stimulates bone formation and resorption and can increase or decrease bone mass, depending on the mode of administration. Continuous infusions, which result in a persisting raised PTH concentration, lead to greater bone resorption. Preliminary research has shown that a once daily injection of PTH causes only a transient increase in the serum PTH and may increase bone mass and strength.

A clinical trial was designed in the USA to assess the effects of once daily injections of PTH. 1637 post menopausal women, from different centres and different countries, took part in a randomised blind trial. They received PTH or a placebo, by a self-administered injection daily.

a) What are the aims of a clinical trial?

b) What is meant by the term randomised and why was it necessary to enrol this large number of women?
c) Explain why a blind trial was used. What is a placebo?