age-associated changes in calcium homeostasis

Physiology

• decreased plasma 1,25-dihydroxyvitamin D
  • decreased renal 1-alpha hydroxylase activity
    • decreased renal PTH responsiveness
  • decreased vitamin D synthesis by skin
    • decreased sun exposure in the elderly
• decreased intestinal absorption of dietary calcium
  • inadequate dietary calcium & vitamin D intake
    • lactase deficiency & avoidance of dairy products
  • intestinal responsiveness to 1,25-dihydroxyvitamin D is diminished
  • gastric acid secretion is diminished
• increased plasma PTH
  • slight decrease in plasma calcium
  • decrease renal clearance of PTH

More general terms

• age-associated changes in the endocrine system