Bones, Calcium, and Osteoporosis
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Bones, Calcium, and Osteoporosis
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Bone• Bone is living, constantly remodeled• Reservoir of Calcium– Calcium levels of blood take precedence over bone
levels– Under influence of
• Calcitonin• Parathyroid hormone• Vitamin D
– Calcium cycle• Absorbed from intestine• Excreted in urine• Absorbed and resorbed from bone
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Bone Disorders Related to Calcium• Rickets– Defective bone growth from lack of Vitamin D– Deformities due to softened bone
• Osteomalacia: Adult form of rickets• Paget’s Disease– Increased Bone resorption– Replacement with abnormal bone– Most asymptomatic
• Fractures, deformities, deafness• Osteoporosis: Demineralization of bone
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Osteoporosis• Demineralization of bone with age• Demographics– 10 million outright, and 34 million with osteopenia
• Women: 80%• Men 20%
• Pathophysiology– Maximum bone density ~30 years– Stable until ~50– Decreases after 50, accelerated for women 1% vs 2-3%– Decreased bone deposition occurs with age– Loss of calcium deposits and density leads to fragility
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Osteoporosis
• Manifestations– Loss of height– Kyphosis, scoliosis– Increased risk of fracture• Wrist fractures• Compression fractures• Femoral neck
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Osteoporosis• Evaluation– X-ray: typically once a fracture is suspected– BMD: Dua-energy x-ray absorptiometry (DEXA)
• Results reported in standard deviations• 1SD = 10% bone loss• 1 – 2SD bellow normal = ostopenia• < 2.5SD = osteoporosis• Site of measurement: wrist, vertebrae, femoral neck• BMD is higher predictor of fracture risk than BP of stroke
– Family Hx of osteoporosis– Personal hx of fractures– Propensity to fall
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Osteoporosis
• Treatment– Prevention!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!– Prevent bone loss– Promote bone formation
• All three require adequate calcium and vitamin D!!!!!!!!!!!!!!!!!!!!!!!!!!
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Calcium salts
• Indications– Mild hypocalcemia– Osteopenia, osteoporosis
• Adverse effects– Hypercalcemia with chronic high doses– Interactions with some drugs
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Calcium Salts: Dose/AgeAge Adequate Level of Calcium Intake
9 – 18 1300 mg daily
19 – 50 1000 mg daily
> 51 1200 mg daily
• Must take into account elemental calcium• Calcium carbonate (most common)• Calcium citrate (best absorbed)• Calcium gluconate (most common IV form)
• Orally: no more than 600mg at one time
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Vitamin D
• Sources: Sun and Fortified Milk– Older adults often do not get enough Vitamin D– Osteoporosis treatment should include Vitamin D
supplementation
– http://www.medscape.com/viewarticle/541149– http://ods.od.nih.gov/factsheets/vitamind.asp
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Calcitonin (Miacalcin)
• Injection or nasal spray• Inhibits osteoclasts• Inhibits resorption of calcium in kidney.• Used for– Treatment of osteoporosis, but not prevention– Hypercalcemia
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Biphosphonates
• Structural analogs of pyrophosphonate• Inhibit resorption of bone• Therapeutic uses– Postmenopausal and glucocorticoid osteoporosis– Paget’s disease
• Preparations: 6 on market– Alendronate (Fosamax) (weekly or daily)– Actonel (weekly or daily)– Boniva (monthly)
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Biphosphonates
• Administration considerations– Must give on empty stomach (OJ or coffee decreases
absorption by 60%)– Must stay upright for 30 minutes afterward (GI upset)– Can be given either daily or weekly– Do not chew or suck on tablet– Full glass of water (min 8 oz)
• Adverse effects– Esophagitis
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Raloxifene (Evista)
• Selective Estrogen Receptor Modifiers• Mimics estrogen in bone, lipids, blood clotting• Blocks estrogen effects: breast and endometrium• Postmenopausal Osteoporosis• Adverse effects– Fetal Harm– Not for use in women who can become pregnant– Caution in patients who smoke: DVT– Hot flashes
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Teriparatide
• Parathyroid hormone• Only drug that increase bone formation• If given continuously causes bone loss• If given intermittently causes bone formation