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54 Cards in this Set
- Front
- Back
T or F: Intrinsic bone diseases present w/ serum Calcium abnormalities
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FALSE
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name 4 intrinsic bone diseases
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osteoporosis
osteogenesis imperfecta osteopetrosis Paget disease |
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T or F: Extrinsic bone diseases often present w/ serum Ca2+ abnormalities
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TRUE
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name 4 extrinsic bone diseases
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primary hyperparathyroidism
secondary hyperparathyroidism osteomalacia/rickets renal osteodystrophy |
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what is the primary purpose of PTH?
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increase serum Ca++
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what is the action of PTH on bone?
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increases Ca++ release
increases PO4--- release |
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what is the action of PTH in the kidney?
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increases Ca++ resorption (in the distal tubule)
decreases PO4 resorption This is how you get a net increase in serum Ca++ |
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what is the action of PTH in the gut?
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indirectly increases Ca++ absorption
Note: No direct effects |
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where are the PTH receptors in the bone?
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on the osteoblasts
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how does PTH lead to the stimulation of osteoclasts?
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osteoblasts secrete osteoclast activating factors (OAFs) when PTH is bound
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In normal Ca++ homeostasis, what compensates for small fluctuations in serum Ca?
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Lining Cell-Osteocyte Complex (LCOC)
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what happens if the threshold of the LCOC is surpassed?
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the Bone Multicellular Unit (BMU) is recruited to raise serum Ca++ often at the expense of the structural integrity of the bone
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define osteopenia
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a general term used to refer to states of low absolute amounts of bone mineral (this includes osteoporosis and osteomalacia)
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define osteoporosis
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there is normal mineralization in a decreased amount of total bone
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define osteomalacia
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decreased mineralization of a normal amount of total bone
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a state of high absolute amounts of bone mineral -->
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osteosclerosis
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a disease state characterized by an increase in the number of BMUs is __ and is seen in __ and __
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high turnover osteoporosis seen in hyperPTH and postmenopausal bone loss
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__ is characterized by a normal number of BMUs but impaired recruitment of osteoblasts.
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low turnover osteoporosis
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__ occurs in normal aging and accounts for the bone losses seen in men and women as they get older
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low turnover osteoporosis
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at physiologic or slightly elevated levels of PTH __ responds by increasing the efflux of Ca++ from bone
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LCOC
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subperiosteal bone resporption and large cystic lesions referred to as Brown tumors -->
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high turnover osteoporosis
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stones, bones, groans, psych overtones -->
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hyperparathyroidism
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what is the most common cause of hypoPTH?
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damage or removal of the PTH glands during surgery
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decreased serum Ca++, increased serum PO4, decreased urinary PO4 excretion -->
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hypoPTH
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what is pseudohypoparathyroidism?
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then the kidneys and bone can't respond to PTH --> hypoCa++ and hyperPO4 occur despite elevated PTH
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What are some features of Albright hereditary osteodystrophy?
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pseudohypoPTH, short stature, round facies, shortened 4th fingers
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ergocalciferol -->
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D2
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cholecalciferol -->
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D3
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in what range are serum levels of Ca++ in pts w/ Vit D deficiency?
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low-normal
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for normal hydroxyapatite formation, the product of the serum __ and __ must exceed __
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Ca++ * PO4 > 30
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when Ca * PO4 < 30 what occurs?
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osteomalacia (decreased mineralization in a normal amount of bone)
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what are the histological hallmarks of osteomalacia?
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widened osteoid seams in regions of bone remodeling
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in skeletally immature pts, osteomalacia is referred to as __
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rickets
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in early stage renal failure, what happens to serum PO4 levels?
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they increase
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how does renal disease lead to secondary hyperparaPTH (osteomalacia)?
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high serum PO4 directly stimulates release of PTH, inhibits hydroxylation of VitD and directly lower serum Ca++ levels
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what is renal osteodystrophy?
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the combination of secondary hyperPTH, osteomalacia, and osteosclerosis
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mineralization of previously osteomalatic bone leads to __
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osteosclerosis
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what is the most common metabolic bone disease?
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involutional osteoporosis
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T or F: postmenopausal osteoporosis is characterized by greater loss of cortical bone over trabecular
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FALSE
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post menopausal osteoporosis: high or low turnover state?
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high
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vertebral and Colles fractures -->
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postmenopausal osteoporosis
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vertebral and proximal femur fractures -->
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age-related osteoporosis
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T or F: hyperthyroidism can cause secondary osteoporosis
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TRUE
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what would serum Ca++ in thyrotoxicosis?
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elevated!!!
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osteogenesis imperfecta results from the inability to form __
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Type 1 collagen
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the __ result from a primary defect in osteoblastic function in which the cells form abnormal extracellular glycoproteins
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mucopolysaccharidoses
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what is the inheritance of the most common OI?
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AD
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what is the primary defect in osteopetrosis?
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lack of osteoclastic bone resorption
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why are pts w/ osteopetrosis prone to infection?
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b/c they lose marrow space
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high alk phos w/ normal Ca++ and PO4 with rapid remodelling -->
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Paget's Disease of Bone
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primary or secondary hyperPTH: hypophosphatemia
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Primary
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hyperCa++ and hypoPO4 -->
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primary hyperPTH
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what is an example of an osteoclast activating factor you should know for a test?
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Rank ligand
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what is the main mechanism of steroid-induced osteoporosis?
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osteoblast precursor inhibition
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