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age-associated changes in calcium homeostasis
Physiology:
1) decreased plasma 1,25-dihydroxyvitamin D
a) decreased renal 1-alpha hydroxylase activity
- decreased renal PTH responsiveness
b) decreased vitamin D synthesis by skin
- decreased sun exposure in the elderly
2) decreased intestinal absorption of dietary calcium
a) inadequate dietary calcium & vitamin D intake
- lactase deficiency & avoidance of dairy products
b) intestinal responsiveness to 1,25-dihydroxyvitamin D is diminished
c) gastric acid secretion is diminished
3) increased plasma PTH
a) slight decrease in plasma calcium
b) decrease renal clearance of PTH
General
age-associated changes in the endocrine system
References
- Geriatric Review Syllabus, 8th edition (GRS8)
Durso SC and Sullivan GN (eds)
American Geriatrics Society, 2013