Bone density test is recommended in all women over the age of 65; women with any of the following risk factors should be screened at an earlier age:
For patients who are likely to be on prednisone 5 mg qd or more for > 3 months, anticipate bone loss. Give a bisphosphonate plus calcium and D.
- Maternal hip fracture after age 50
- Current smoker
- Body weight less than 56.3 kg (124 pounds)
- History of fracture after age 50
- Needs to use arms to rise from a chair
- Receiving (or about to start) long-term (> 3 months) oral corticosteroid therapy
- Use of anti-seizure medications like phenytoin, phenobarbital, carbamazepine, primidone, valproic acid(accelerate bone lose by 70-80%)
- Hyperthyroidism or excess thyroid hormone use. Note that use of thyroid hormone to maintain a euthyroid status is NOT a risk for bone loss
- Use of vitamin D in excess of 2000 IU/d increases bone resorptoin
- Prolonged use of vitamin A in doses > 10,000 IU/day stimulates bone resorption and inhibits bone formation
- Use of cyclosporine, tacrolimus and methotrexate in higher doses can increase bone resorptoin
HPHC offers the following risk factors (which warrant DEXA bone density scan between ages 47 and 64):
- Chronic steroid use
- Chronic use of seizure medication
- Bilateral oophorectomy and no current hormone use
- Tobacco dependence or COPD
- Fracture (other than skull, face, fingers, toes)
- Recent discontinuation of estrogen therapy
Changes in BMD of < 4% in the vertebrae and 3-6% in the hip are within the range of the inherent measurement error of the DEXA scanners. Alendronate and residronate increase LS BMD by 5-7% and hip BMD by 3-6% when used for about 3 years. Alendronate use for 10 years has been associated with an increased BMD of 14% in the LS spine and 7% in the hip (5.4% in femoral neck). The frequency of testing BMD should be no more than every 2-3 years. Whether it is useful to test patients currently on therapy with a bisphosphonate is unclear.
Who should be treated?: The National Osteoporosis Foundation recommends initiating therapy in women with T-score of <= -2.0 by hip DEXA and no risk factors OR those with a history of low-trauma hip or spine fractures. Women with one or more risk factors should be treated if they have a T-score < -1.5.
WHO criteria should not be applied in the diagnosis of osteoporosis in premenopausal women, and the Z-scores rather than T-scores should be used. The International Society for Clinicial Densitometry states that the diagnosis of osteoporosis in this group requires low BMDs and a secondary cause (diagnosis should never by based on BMD scores alone).
Monitoring treatment: There is some controversy about monitoring, as it is quite unclear what to do with a woman whose bone density is falling in spite of bisphosphonate treatment. If we don't know what to do, why bother checking FU DEXA scans? This is the current debate (as of 12/05 - see Johns Hopkins Advanced Studies in Medicine 5:547, editorial by Rosenfeld in 11/05).
Evaluation of patients with osteoporosis:
Basic testing in most patients with osteoporosis includes a chemistry profile (including electrolytes, blood urea nitrogen, creatinine, calcium, magnesium, phosphorus, alkaline phosphatase, protein and albumin), complete blood count, and serum thyrotropin (TSH) measurement. Measurements of markers of bone turnover for diagnostic purposes are not recommmended.
There are patients in whom the history, physical examination, or initial laboratory data reveal features suggestive of other contributing diseases:
- Normal serum bicarbonate, calcium, TSH, and creatinine values exclude potentially treatable conditions such as metabolic acidosis, hyperparathyroidism, hyperthyroidism, and renal insufficiency.
- Normal serum calcium, albumin, phosphate and alkaline phosphatase values mitigate against osteomalacia; a normal blood count coupled with normal total serum protein, calcium, and creatinine concentrations makes multiple myeloma unlikely.
- The serum alkaline phosphatase concentration may be high in patients with healing fractures. Thus, an isolated high value in a patient with a recent fracture is of limited diagnostic value.
- Serum testosterone should be measured in men with osteoporosis, especially if they have diminished libido, impotence, or testicular atrophy.
- If patients have a generous vitamin D intake (>800 IU/day) and no conditions interfering with vitamin D absorption or metabolism, it may not be necessary to measure serum 25-hydroxyvitamin D. In one study bone mineral density was higher and fracture rates lower in patients whose vitamin D intake was greater than or equal to 800 IU/day, regardless of the serum 25-hydroxyvitamin D concentrations. Others suggest measuring 25-hydroxyvitamin D levels in all patients, even healthy patients taking 800 IU of vitamin daily. This argument is based upon data suggesting that PTH begins to rise with 25-hydroxyvitamin D levels lower than 30 ng/mL, which can be seen even in those taking 800 IU of vitamin D daily.
- Serum 25-hydroxyvitamin D and PTH should be measured if the patient is elderly with poor vitamin D intake or if there is a history of gastrointestinal disease (such as malabsorption or gastrectomy), liver disease, or anticonvulsant drug therapy. It should also be considered in individuals living in northern latitudes given the prevalence of vitamin D insufficiency in these areas. Vitamin D deficiency is associated with low serum 25-hydroxyvitamin D and high serum PTH concentrations due to secondary hyperparathyroidism. For those with mild to moderate vitamin D deficiency due to limited sun exposure or poor diet, 50,000 Units or ergocalciferol taken once per week for 6 weeks is suggested by some authors (twice per week if vitamin D < 8 ng/ml). In severe deficiency, PTH and serum calcium levels my be abnormal. Repeat labs at 6-8 weeks after supplementation (serum PTH costs about $90, and vitamin D level costs about $80).
- Urinary cortisol excretion should be measured or an overnight dexamethasone suppression test should be done if Cushing's syndrome is suspected.