Patients with severe secondary hyperparathyroidism, usually associated with osteitis fibrosa on bone histology, show considerable resistance to Epoetin, partly because of replacement of the cellular components of the bone marrow by fibrous tissue. In case of unexplained resistance to Epoetin, investigation of secondary hyperparathyroidism is strongly recommended, with measurement of serum parathyroid hormone, calcium, phosphate, and alkaline phosphatase levels and, where needed, skeletal radiology and bone biopsy. Treatment of severe secondary hyperparathyroidism consists of active vitamin D metabolites or parathyroidectomy, although the marrow fibrosis, if present, may be irreversible. The finding of a progressive inability of the bone marrow to respond to Epoetin treatment with higher levels of parathyroid hormone suggests the importance to prevent metabolic bone disease and in particular secondary hyperparathyroidism. Moreover, there are several reports of a beneficial action on hemoglobin levels of an effective treatment of hyperparathyroidism. Larger, controlled studies are necessary to confirm these preliminary and exciting findings, and to elucidate the mechanisms underlying the improvement in anemia after medical or surgical treatment of hyperparathyroidism.
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