Pathophysiology and diagnosis of primary hyperparathyroidism--strategy for asymptomatic primary hyperparathyroidism

Primary hyperparathyroidism (PHPT), the most common cause of hypercalcemia due to excessive secretion of PTH, is usually associated with hypophosphatemia and elevated serum chloride. Although PHPT was often complicated by renal stone disease and osteitis fibrosa in the past, routine screening of serum calcium (Ca) and development of sophisticated assay of parathyroid hormone have contributed to earlier detection of asymptomatic PHPT (APHPT). The proportion of APHPT patients, who have a mild elevation of serum Ca levels, usually within 1.0 mg/dL above the upper limit of normal, rose from 10-20% to approximately 45% of all PHPT patients in 1990-1995 in our clinic. Although it has been reported that the prevalence of PHPT is about 0.1% of the American population, the prevalence of PHPT appears to be far less in the Japanese population. Determination of a strategy for the increasing number of APHPT patients, is a pressing need but has yet to be accomplished. Treatment with bone antiresorptive drugs has met with some success, although the long-term efficacy of this treatment is not clear. The therapeutic effects of Ca-sensing receptor agonists appear promising.