Osteoporosis

Low bone mass and microarchitectural deterioration leading to increased fracture risk. The diagnosis may be made clinically, or on bone densitometry scanning.

Baseline investigations - all patients

Full blood count

This is a useful indicator of general health and underlying disease, for example normocytic normochromic anaemia may be seen in rheumatoid arthritis and pituitary failure.

Urea and electrolytes

Hypokalaemia may occur in glucocorticoid excess.

Liver function test

Chronic liver disease is a risk factor for osteoporosis.

Bone profile

Primary hyperparathyroidism is a recognised risk factor for osteoporosis. Hypercalcaemia may also occur with malignancy.

Hypocalcaemia may indicate vitamin D deficiency.

Vitamin D

Vitamin D deficiency is common and should be treated with pharmacological replacement doses, rather than standard supplementation.

Thyroid stimulating hormone, free thyroxine

Long term suppression of TSH increases the risk of osteoporosis, though does not necessarily imply overt thyrotoxicosis.

Elevation of thyroxine with a low TSH demands treatment for thyrotoxicosis.

Testosterone, sex hormone binding globulin

In men presenting with osteoporosis, testosterone should be assessed early morning on at least two occasions, and in conjunction with sex hormone binding globulin, in order to calculate free androgen index.

If this is low, further investigation into the cause of hypogonadism are mandatory, before optimum treatment is determined.

Parathyroid hormone

If hypercalcaemia is documented, the first step in determining the cause is checking PTH level.

Hyperparathyroidism is a recognised risk factor for osteoporosis.

Further investigations - in selected cases

Luteinising hormone, follicle stimulating hormone

It is worth documenting luteinising hormone and follicle stimulating hormone in male patients with a reduced testosterone level, and in women below 50 years with oligomenorrhoea. 

Baseline pituitary function: prolactin, insulin like growth factor I, 9am cortisol

In hypogonadal patients, and those with possible pituitary disease, full baseline pituitary function should be assessed and further investigation of hypopituitarism considered.

2x24hr urinary free cortisols

If Cushing’s syndrome is suspected clinically, UFCs are a sensitive but not specific initial screen.

Low dose dexamethasone suppression test

Dexamethasone suppression testing should also be performed in all patients with suspected Cushing's.

Bone densitometry scan

This is not required in all cases, as many patients will have a confirmed diagnosis of osteoporosis on clinical grounds.

Bone densitometry scanning is very useful in the risk stratification of those suspected to have, or with multiple risk factors for osteoporosis but who have not sustained any low impact fractures.

Plain radiography of affected or painful areas

Plain radiography can be useful to determine the likely cause for example of back pain and to aid interpretation of denitometry scans. For example, if vertebral bone density is surprisingly high, this may be due to vertebral collapse which should be evident on plain films.