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Osteoporosis

General

Risk of fracture increases by 2-3 if bone density more than 1sd from mean. 10% of women and 50% of men have a secondary cause.

Bone mass

Risk factors for bone loss

Hormonal
- Menopause
- Early menopause
- Oophorectomy
- Amenorrhoea
- Premenopausal oestrogen deficiency
- Nulliparity
Lifestyle
- Increasing age
- Immobility
- Cigarette smoking
- Alcohol
- Caffeine
- Strict vegetarians
- Excessive thinness or anorexia nervosa
- Endurance athletes with amenorrhoea
Genetic
- FH of osteoporosis
- Short stature
- Being female
Diseases
- Cushing's
- Steroid therapy
- Hyperthyroidism
- Diabetes type 1

Secondary causes of osteoporosis

Common
- Drugs
- Immobility
- Old age
- Menopause
Less common
- Excess corticosteroids
- Malabsorption
- Hypogonadism
- Chronic liver disease
- Organ transplantation
Rare causes
- Mastocytosis
Chromosomal
- Turner's syndrome
Endocrine
- Cushing's
- Thyrotoxicosis
- Acromegaly
- Diabetes type 1
- Primary hyperparathyroidism
Inherited
- Osteogenesis imperfecta
Drugs
- Glucocorticoids
- Thyroxine
- Heparin
- furosemide
- Cytotoxics

Testing for secondary causes of osteoporosis

Secondary causes of osteoporosis are present in about 30% of women and 55% of men with vertebral crush fractures
Tests to exclude secondary causes include
- full blood count and erythrocyte sedimentation rate,
- bone biochemistry (serum calcium, phosphate, and alkaline phosphatase concentrations),
- liver and kidney function tests,
- serum thyroid stimulating hormone, and
- coeliac serology
In patients with vertebral fractures myeloma should be excluded using serum protein immunoelectrophoresis

Testing for secondary causes of osteoporosis (2010)

Protection

OC
Pregnancy

Adequate calcium intake is 800mg/day (1500mg/day post menopausal) but most adults only achieve 500mg/day. Calcium supplementation amy be useful when dietary intake is low and physical activity high. It is not a substitute for HRT postmenopausally, but may have a small place in the prevention of hip (not vertebral) fractures. Chewable or effervescent tabs give most reliable absorption. 2 pints of milk contain 1500mg calcium.

Pointers

Steroids>6months
Atraumatic fracture (Radiological osteopoenia)
Osteoporosis risk factor scoring

Identification

Dual Energy Xray Absorptiometry (DEXA)

Relative risk of skeletal sites can be predicted: 1sd decrease in bone mineral density increases

fracture risk by 200%
hip fracture risk by 300%
forearm fracture risk by 230%

Interpreting DEXA Results

DXA results are reported as T scores (comparison with the young adult mean) and Z scores (comparison with reference values of the same age). The T score relates to absolute fracture risk whereas the Z score related to the individual’s relative risk for their age. The table below shows a simple classification of DXA results and guidance for management:

T score (WHO standard reference)	Fracture Risk	Action
Normal T > -1.0	Low	Lifestyle advice
Low bone mass (osteopenia) T –1.0 to –2.5	Above average	Lifestyle advice. HRT especially in women aged 50 – 60 years. Calcium and vitamin D supplementation.
Osteoporosis T< -2.5 Treat	High	Lifestyle advice Calcium and vitamin D supplementation
Established osteoporosis T < -2.5 plus one or more fractures	Very high	Lifestyle advice. Pain control. Exclude secondary causes. Treat (see below). Calcium and vitamin D supplementation. Consider referral.

WHO classification of osteoporosis

	Bone mineral density*	T score	Prevalence (%)
Normal	<1 SD	>–1	20
Osteopenia (or low bone mass)	1-2.5 SD	–1 to –2.5	52
Osteoporosis	2.5 SD	–2.5	28

*Below the young adult mean.

In white women older than 50 years.

Brad Cheek: last updated Dec 2010
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