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Bisphosphonates
Chvosteks Sign
Calcium
Ectopic PTH Production
Parathyroid Adenoma
Phosphate
Trouseaus Sign
Vitamin D
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- Calcium released from sarcoplasmic reticulum in stimulation of skeletal
and cardiac muscle
- calcium released from mitochondria in secretory cells
- calcium comes in through intestine, some is lost due to enteric secretion
- excreted in urine
- resorped and deposited in bone reshaping
- must be kept constant in blood.
- in growing period, deposition in bone > resorption of bone therefore
gradual loss from blood
- replaced by decreased excretion in urine and intestine
- principally controlled by:
- androgens favour bone formation in childhood and puberty
- estrogen inhibits PTH-mediated bone resorption in adult female
- glucocorticoids necessary normally for skeletal growth
- in excess decrease renal tubular calcium reabsorption
- interfere with intestinal calcium absorption
- stimulate PTH secretion
- inhibit normal osteoblastic bone growth
- inhibit gonadal androgens
- thyroid hormones
- too little causes retarded bone development
- too much causes excessive bone resorption and hypercalcemia may lead
to osteoporosis
- growth hormone
- acts through IGF-I (produced in liver and bone)
- causes mitosis in chondrocytes and osteoblasts
- also increase intestinal calcium absorption and renal phosphate
reabsoption
14.7 HORMONES INFLUENCING CALCIUM, PHOSPHATE, BONE
| distribution of calcium: intracellular, plasma,
interstitial fluid, bone. |
phosphate, Mg homeostasis |
| calcium fluxes via diet, kidney. |
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| systemic effects of lowered and raised plasma calcium |
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special considerations calcium homeostasis: development,
pregnancy, lactation, renal failure |
1.1.4 Other hormones that act on bone:
| glucocorticoids — as cause of osteoporosis |
bone resorption in malignancy — PTH-RP |
| sex steroids — post-menopausal osteoporosis |
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| thyroid hormone, growth hormone & IGFs, local growth
factor |
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