ABSTRACT
Hyperphosphatemia is a relative term. As pediatricians are well aware, serum Pi levels vary considerably with age. The highest levels occur during periods of rapid growth and bone mineralization; levels decline to the adult range after the adolescent growth spurt is completed.1 Despite the higher Pi levels in childhood blood calcium concentrations are maintained in the normal range, thus the CaxPi product remains sufficiently high to permit bone mineralization to proceed.1 This physiological relative hyperphosphatemia is reflected by an increase in the serum levels of the osteoblastic markers alkaline phosphatase and osteocalcin.1"4 Such growth-related hyperphosphatemia is also correlated with elevations in the dihydroxyvitamin D (calcitriol), growth hormone (GH), insulin-like growth factor 1 (IGF-1) and sex steroids.'•5~7 In contrast to androgens, estrogen levels are inversely related to serum Pi values.8
