Endocrinology Metabolism

Vitamin D in Osteoporotic patients

Management and Treatment of the Disease

My patient with osteoporosis has a 25-hydroxyvitamin D level of 20 ng/ml. Is that enough?

For the population in general, a 25-hydroxyvitamin D level of 20 ng/ml was considered adequate by the Institute of Medicine. For your patient with osteoporosis a higher target is more appropriate because:

  • Patients often do not take vitamin D supplements regularly

  • Some vitamin D assays may overestimate the level

  • As patients become more obese, the volume of distribution increases, which may lower the level

  • In one study, to eliminate all evidence of osteomalacia on bone biopsy, a vitamin D level of 30 ng/ml was needed

  • Some studies show that a vitamin D level of 30 ng/ml is needed for optimal response to bisphosphonate therapy for osteoporosis.

For the osteoporosis patient 30 ng/ml is a reasonable target. There is no evidence that this level is dangerous.

The Institute of Medicine stated that the general population needs 600-800 units daily in diet plus supplements. They also stated that up to 4000 units daily was probably safe. While toxicity is definitely noted at levels of about 100 ng/ml (hypercalciuria and hypercalcemia), there is controversy about levels beyond 40 ng/ml. Thus, patients should know that more is not necessarily better.

What is the best way to give my osteoporosis patient vitamin D?

Cholecalciferol (Vitamin D3) is readily available over the counter in 400 international unit, 1000 international unit, and 2000 international unit tablets or capsules. It is inexpensive and can be taken daily. For the osteoporosis patient, the serum 25-hydroxyvitamin D level should be measured and the dose adjusted so that the patient attains a level of 30 ng/ml.

An alternative is to use ergocalciferol (Vitamin D2), which is available by prescription as a 50,000 international unit capsule. To increase the vitamin D level quickly, the patient can take 50,000 units weekly for 4 to 12 weeks and then maintain the level with a monthly capsule. Occasional patients will need 50,000 units every 2 weeks to maintain a level of 30 ng/ml.

Do not give larger doses of vitamin D at one time. There are studies showing that 500,000 units once yearly actually increases risks for falling.

My patient has sarcoidosis. Is vitamin D dangerous in this case?

Some granulomatous diseases, such as sarcoidosis, can produce hypercalciuria and hypercalcemia because the granulomas may contain the 1-alpha hydroxylase that activates 25-hydroxyvitamin D. This unregulated production of calcitriol leads to increased gut absorption of calcium, hypercalciuria and even hypercalcemia. Thus, the patient with active granulomatous disease must be monitored more carefully than the typical patient with osteoporosis. In addition to the 25-hydroxyvitamin D level, a 24-hour urine for calcium and creatinine and serum calcium must be followed as you carefully increase the 25-hydroxyvitamin D level. Other granulomatous disorders that can lead to hypercalcemia include lymphoma and tuberculosis. In some cases it is helpful to measure 1,25-dihydroxyvitamin D, especially in the evaluation of hypercalcemia of unknown etiology with low serum PTH.

Does vitamin D prevent osteoporotic fractures?

In a meta-analysis, vitamin D with calcium had a modest effect in reducing fracture risk. For most patients with osteoporosis, further pharmacologic therapy is necessary. A very recent analysis concluded that at least 800 international units daily were necessary to prevent fractures.

A recent study found a correlation between vitamin D levels and strength of the femoral neck. Nonetheless, there is still controversy about the efficacy of vitamin D to prevent or treat fractures; most studies are of vitamin D plus calcium. For osteoporosis patients now, follow the IOM recommendations as modified by other experts to assure about 1000 to 1200 mg of elemental calcium and a 25-hydroxyvitamin D levels of 30 ng/ml.

My patient wants to take mega-doses of vitamin D to prevent cancer and heart disease. What do I advise?

More is not better. Indeed, just like the patient with sarcoidosis, excess vitamin D ingestion by your patient may lead to hypercalciuria (possibly kidney stones) and hypercalcemia. For the osteoporosis patient, aiming for a 25-hydroxyvitamin D level of 30 ng/ml is reasonable and safe.

There is epidemiologic evidence suggesting that lower levels of vitamin D may be associated with heart disease, cancer, diabetes, and multiple sclerosis. However, such studies generate hypotheses that need to be proven by clinical trials. At this point, there is tantalizing evidence that these associations are important, but little evidence that vitamin D levels beyond 30 ng/ml will prevent disease.

Some large trials are planned or are in progress that we hope will provide definitive answers.

Tell your patient that for now, if she has osteoporosis, 30 ng/ml is a safe target for the 25-hydroxyvitamin D level. She will definitely not be deficient if this is her level. We need more studies to learn the potential benefits and harms of higher target levels.

I have heard that low vitamin D levels are associated with stress fractures in younger people. Is this true?

Studies in military recruits have generally demonstrated that young individuals with the lowest 25-hydroxyvitamin D levels and the poorest physical condition upon starting boot camp have the greatest chance of a stress fracture. A recent study from the UK confirms that low vitamin D levels predict risk of stress fracture in military recruits.

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