OSTEOPOROSIS
Dr John Hinnie
Consultant in Diabetes, Endocrinology and General Medicine
Royal Alexandra Hospital, Paisley, Scotland, PA2 9PN
Osteoporosis is a very common disease associated with pain, fracture, disability and death. Osteoporotic fractures typically occur at three main sites - hip, vertebrae and wrist. In the UK approximately 70,000 hip, 120,000 vertebral and 50,000 wrist fractures occur annually.
Osteoporosis has been defined by the WHO as "a progressive systemic skeletal disease characterized by low bone mass and microarchotechtural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture". It can also be defined in terms of Bone Mineral Density (BMD) as measured at the hip or lumbar spine by DEXA (Dual Energy X-ray Absorptiometry). Bone density as measured by DEXA can be expressed as a Z or T score which define how many standard deviations an individual's bone density differs from a standard population. A young adult population is used for the T-score and an aged matched population is used for the Z-score. Osteoporosis has been defined by the WHO as a T-score of below - 2.5 at the hip or spine in women.
Causes
By far the most common cause of osteoporosis is post menopausal oestrogen deficiency in women. However many other conditions can result in osteoporosis.
Some secondary causes of osteoporosis
Endocrine: hypogonadism, hyperparathyroidism, hyperthyroidism,
Cushing's syndrome
Drugs: glucocorticoids
Metabolic: malabsorption, chronic renal failure, chronic liver failure
Others: osteogenesis imperfecta, multiple myeloma
It follows that a patient with osteoporosis needs the following investigations.
Investigation
| Haematology: | full blood count and ESR |
| Biochemistry | urea and electrolytes, liver function tests calcium, phosphate, alkaline phosphatase thyroid function tests luteinising hormone, follicle stimulating hormone, oestrogen/testosterone vitamin D |
| Radiology |
It is probably worthwhile carrying out thoracolumbar spine X-rays if osteoporosis is suspected since this will detect any vertebral fractures and allow you to recognise any new fractures in the future conventional radiology is not a good method for assessing bone density since technical factors such as exposure will influence the radiodensity of bone, so that at best only qualitative assessment of bone density can be obtained in this way |
| DEXA | as discussed previously, this can be used to gain a quantitative assessment of bone density |
Identification of patients at risk of osteoporosis:
Several factors should alert you to the possibility of osteoporosis in a patient. A history of fracture caused by minor trauma, X-rays suggestive of osteoporosis,
strong family history of osteoporosis, loss of height or kyphosis, long term steroid use or any of the possible causes of secondary osteoporosis should raise your index of suspicion.
If in doubt about the presence of osteoporosis consider a bone densitometry scan.
Address the factors which may cause secondary osteoporosis, (e.g. hyperparathyroidism, vitamin D deficiency, malabsorbtion, thyrotoxicosis), then consider treatment.
Treatment of osteoporosis
HRT if appropriate in hypogonadal or postmenopausal women.
Testosterone in hypogonadal men
Oral Bisphosphonates e.g.
- Alendronate 10 mgs per day (alternatively as 70 mgs Fosamax "once weekly")
- Risedronate 5 mgs per day
In postmenopausal women, where HRT is not feasible, Raloxifene (60 mgs per day) may be a suitable alternative.
Where calcium and vitamin D intake is low, supplements should be given e.g.
Calcichew D3 Forte - 1 tablet twice daily
Adcal D3 - 1 tablet twice daily
Where drug therapy is not possible, calcium and vitamin D therapy alone (as outlined above) have been shown to decrease fracture rates, and should therefore be given