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42 Cards in this Set
- Front
- Back
What does serum calcium help maintain?
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NM transmission, blood coagulation, muscle contraction, cardiac function, cell membrane permeability
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What form of serum calcium is physiologically active?
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Free, unbound, ionized calcium
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What decreases calcium absorption?
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Age, estrogen decline
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How is PTH release regulated?
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Inversely regulated by CaSR, a GPCR that detects Ca levels. Release when hypocalcemia, inhibited with hypercalcemia
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What are normal levels?
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8- 10 (14 fatal)
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What are the three main actions of PTH?
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1. promotes renal tubular reabsorption of Ca (decreases excretion)
2. Increases resorption of Ca and phosphorus from bone and increases mobilization 3. promotes renal synthesis of 1,25-(OH)2-Vit D active form |
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How does PTH increase resorption of Ca and phosphorus from bone?
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stimulates RANKL ligand by osteoblasts, acting on RANK promotes osteoclast formation and activity --> both resorption and formation
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What does excess PTH do versus low pulsatile?
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resorption vs bone formation
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What is the major regulator of Ca in the intestines?
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1,25-(OH)2-Vit D
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What form of vit D is the mammalian derived product?
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D3 or cholecalciferol
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What important concept of the vit D pathway is needed to determine treatment for vit D, Ca, or phosphate issues?
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The mechanism for treatment depends on the location of problem in pathway, ie if renal failure, give 1,25-(OH)2 D3 and not anything else cause cant convert
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Vit D3 is produced in the skin from ___ under influence of ___?
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cholesterol; UV light
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What is the pathway?
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vit D -> in skin --> D3 --> stored in fat --> liver --> calcifediol (most abundant) --> kidney --> calcitriol (active)
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What promotes/inhibits production of calcitriol?
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PTH, low levels of Ca or phosphate; inhibited by itself
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What are the actions of calcitriol?
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induces absorption of Ca and phosphate in intestines; induces RANKL; decreases excretion. Mostly same as PTH
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Where is calcitonin produced and half-life?
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parafollicular C cells of thyroid; 10 min
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What is secretion promoted by?
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Hypercalcemia
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What are the two main actions of calcitonin?
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increases excretion and inhibits bone resorption by osteoclastic and osteocytic cells
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Does calcitonin have Ca resorption effects in the intestine?
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no
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What is the most common metabolic bone disease and 2 causes of elderly morbidity?
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osteoporosis; "Dowagers hump" loss of height due to spine collapse, hip fractures
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When is estrogen replacement therapy used for osteoporosis and what caveat should be remembered?
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postmenopausal; it does not reverse bone loss, just prevent it; increases breast cancer and heart disease
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What SERM reduces new vertebral fractures by 30% and 50% with no previous fractures?
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Raloxifene
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What tissues do SERMs exhibit activity at?
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estrogen agonist in bone; estrogen antagonist at breast and uterus
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What is a contraindication for bisphosphonates?
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ulcerative esophagitis
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Which drug is also used in Paget's disease and can improve bone mass in established osteoporosis?
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bisphosphonates
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Which osteoporosis drug is poorly absorbed in the GI?
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bisphosphonates
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How does sodium fluoride work?
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Instead of decreasing bone resorption, it increases osteoblast prolif and formation.
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What does excess fluoride cause?
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bone fragility
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Which drug is a PTH analog and is administered intermittently to those who can't tolerate dronates?
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teriparatide
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Which drugs can cause drug induced osteopenia?
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anticonvulsants, chronic glucocorticoids, and alcoholism
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What would you see in a patient with pseudohypoparathyroidism?
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end organ insensitivity to PTH, normal to high levels of PTH
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What two calcium supplements are used for hypocalcemia?
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oral Ca carbonate and IV Ca gluconate (infants or ER or severe)
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What is the common cause and treatment of primary hyperparathryoidism?
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parathyroid adenomas; surgical removal
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What drug stimulates CaSR and causes a decrease in PTH?
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Cinacalcet
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What precautions should be heeded with cinacalcet
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may cause hypocalcemia, do not use with dronates, etc; be cautious of
CYP3A4 inhibitors |
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Most common cause of hypercalcemia
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Paget's disease; slow virus infection
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Paget's disease causes excessive bone resorption and disorganized remodeling leading to?
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nerve compression; increased bone vascularization, abnormal bone structure
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Treatment of choice for severe Paget's disease and differences between types
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Calcitonin; salmon-derived has longer half life and greater potency, admin through nasal spray, sc or im; human no refractory, admin im or sc
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2 types of bisphosphonates approved for Paget's disease
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Etidronate (older), Pamidronate (newer)
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Cytotoxic antibody treatment used if unresponsive to bisphosphonates and calcitonin?
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Plicamycin (mithramycin)
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What is used in emergency hypercalcemia associated with malignancy?
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plicamycin (mithramycin)
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What are other emergency treatments for hypercalcemia?
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saline infusion with or w/o loop diuretics, calcitonin, prednisone or other steroids,
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