Age, renal tubular phosphate reabsorption, and serum phosphate levels in adults.

A relation between age and serum phosphate levels in adults has been recognized since 1969.1 We used data from the Gubbio Population Study to analyze serum phosphate levels and renal phosphate handling in relation to age in 2107 men and 2560 women (age range, 18 to 97 years). In adults, serum phosphate levels decline with age, except for a transient increase during the perimenopausal period in women. The age-associated decline in serum phosphate levels reflects changes in tubular phosphate reabsorption, which, in turn, might be explained by age-dependent changes in tubular phosphate handling or in its hormonal modulators (e.g., parathyroid hormone, phosphatonins, and growth hormone