AJP - Endocrinology and Metabolism, Vol 272, Issue 1 E139-E146, Copyright © 1997 by American Physiological Society
Aging alters calcium regulation of serum concentration of parathyroid hormone in healthy men
A. A. Portale, E. T. Lonergan, D. M. Tanney and B. P. Halloran
Department of Pediatrics, University of California, San Francisco.
We examined the effect of aging on the relationship between the
concentrations of blood ionized calcium and of serum parathyroid hormone
(PTH) in 22 healthy men [9 elderly (age 74 +/- 2 yr) and 13 young (age 39
+/- 1 yr)] in whom the glomerular filtration rate was > 70 ml/min.
Throughout a 24-h period, serum concentrations of PTH in the elderly men
were twice those in the young men, whereas blood ionized calcium did not
differ between the two groups. With intravenous infusion of calcium
gluconate, the minimum PTH concentration was two- to threefold higher in
the elderly men. With infusion of NaEDTA. the maximum PTH concentration was
20% higher in the elderly men. The calcium set point for PTH release was
higher in the elderly than in the young men (4.71 +/- 0.04 vs. 4.54 +/-
0.03 mg/dl, respectively, P < 0.005). In these healthy men, the
age-related increase in serum PTH could not be attributed to a sustained
decrease in concentration of either blood ionized calcium or
1,25-hydroxyvitamin D. These findings suggest that, with aging, the
relationship between calcium and PTH is altered such that at any given
level of calcium, the concentration of PTH is higher.
