Secondary hyperparathyroidism almost universally accompanies end-stage renal disease (ESRD). In some, but not all studies, elevated serum parathyroid hormone (PTH) concentrations are associated with increased fracture rates, cardiovascular disease, and mortality in ESRD. The serum concentration of PTH required for optimal bone health and reduced cardiovascular risk in such patients remains elusive. Recent clinical trials have failed to show substantial changes in morbidity and mortality following reductions of elevated serum PTH concentrations. In this review, we will assess some of the difficulties in evaluating elevated serum PTH concentrations, and their association with skeletal fractures and mortality in ESRD patients. We are of the opinion that in the context of ESRD, elevated PTH concentrations occur in conjunction with other comorbid conditions such as diabetes mellitus, malnutrition, hypertension, volume excess, preexisting heart disease, all of which have prevented establishing a precise association between elevated serum PTH concentrations and global or skeletal outcomes. Age, gender, and racial variability among groups make interpretation exceptionally difficult. Analysis of prevalent ESRD populations with secondary hyperparathyroidism should take all these factors into account. We suggest that future clinical trials which examine the usefulness of reductions in serum PTH concentrations be conducted in age, sex, and racially balanced groups, without or with minimal coexisting confounding disease. Furthermore, trials in such populations should have as their primary outcome a reduction in fractures rather than an alteration in mortality.
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