Treatment of vitamin D deficient osteomalacia may unmask autonomous hyperparathyroidism.

Two cases of vitamin D deficient osteomalacia with secondary hyperparathyroidism are presented. In both cases treatment with vitamin D replacement therapy resulted in elevated calcium levels and a failure of parathormone levels to normalise, indicating autonomous parathyroid activity. Subsequent surgery in one case resulted in removal of a parathyroid adenoma. The importance of osteomalacia and its complications are discussed.