Severe Hypocalcemia During Treatment for Osteomalacia, with Coeliac Disease


Question

can hungry bone syndrome occurs in severe osteomalacia with immediate large dose replacement of Vitamin D.

Patient has low calcium raised alkaline phosphatase and high level of PTH, twice the upper limit of normal. Also, found to have underlying coeliac disease with low hemoglobin.

should the primary aim be to replenish the calcium with Vitamin D in lower dose to avoid potential risk of hungry bone. Calcium level were as low as 1.3 before being seen by endocrinologist and had treatment by IV with calcium by acute physician and subsequently remained low at 1.7. She is now on gluten free diet.

Once the calcium replete with fall in AlKphos and normalization of calcium, then to consider higher doses upto 5000 IU day or weekly equivalent dose? Dr J Shakher, Consultant Physician, Birmingham, UK

Response

Hungry bone syndrome, or a decrease in serum calcium levels as one promotes a rapid mineralization process in bone that has been chronically aberrant, is not uncommon in the setting of chronic osteomalacia as treatment with vitamin D is being initiated. This complication of therapy can be usually prevented, or at least considerably tempered, by providing generous calcium supplementation during the healing process. If severe malabsorption exists, then parenteral calcium administration may be required.

In your patient, the low calcium, elevations in serum alkaline phosphatase activity, and secondary hyperparathyroidism are typical biochemical findings of severe osteomalacia or rickets. The very low serum calcium values may represent further calcium malabsorption as a consequence of the intestinal disease, as well as the rapid shift of calcium into the mineralizing skeleton. Indeed, the underlying coeliac disease can affect intestinal absorption of both calcium and vitamin D.

To heal rickets or osteomalacia, we usually recommend vitamin D together with calcium to prevent hungry bone syndrome. For vitamin D, this is in the range of 1000- 2000 IU daily in children; in an adult I would suggest 50,000 units twice weekly for 3-4 weeks and then lower to maintenance therapy of 1000 units daily, monitoring the chemistry values indicated. Given that there is coeliac disease you may need to increase this dose, based on resultant 25-OHD levels. However, the critical piece for prevention of hungry bone syndrome is the provision of sufficient calcium. We usually are successful providing this orally, but you will need to employ a product compatible with a gluten-free diet. You can adjust calcium supplementation upwards as to make sure you correct the hypocalcemia. Your severe case may require the use of intravenous calcium, as you have been doing. We generally do not decrease the dose of vitamin D to manage this problem, with the idea of later increases in dose. Thomas Carpenter, MD