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59 Cards in this Set
- Front
- Back
Where is most of the body's calcium? Where is the least?
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Most = skeleton
Least = ionized |
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What are 5 functions of Ca?
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1. Muscle contraction
2. Bone mineralization 3. Coagulation 4. MEmbrane potential 5. Enzyme cofactor |
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Calcium is measured in what forms?
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1. Total
2. Free |
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What are 2 methods for total Ca measurement?
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-Photometric
-Atomic absorption spectrometry |
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Name 2 different photometric methods for calcium:
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1. O-cresolphthalein complexone
2. Arsenazo III |
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-What color does the O-cresolph complexone reaction produce?
-At what pH? -What else has to be done? |
Red color
pH = 10-12 Remove Mg -Competes with 8-hydroxyquinolone. |
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What wavelength is atomic absorption Ca method done at?
What needs to be done for the method? |
-422.7 nm
-Remove Ca from protein w/ acid. -Remove phosphate w. lanthanum. |
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What method is used to measure ionized calcium?
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Ion-selective electrode.
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What is the reference range of:
-Total calcium? -Ionized calcium? |
Total: 2.2-2.6 mmol/L
Ionized: 1.0-1.2 mmol/L |
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What specimens can be used for calcium measurements?
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Serum or heparin whole blood
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What can't be used?
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Citrate, oxalate, EDTA
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What should be done to specimens intended for Ca measurement?
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Remove RBCs right away to prevent Calcium uptake.
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What can alter calcium measurements horribly?
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Gross hemolysis.
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What physiologic measurement needs to be minded in Ca msmt?
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pH; acid pH means more H+ will be on albumin, displacing Ca and increasing the free Ca+ measurement. Vice versa.
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Name four functions of phosphate:
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1. Hydroxyapetite
2. ATP/NADP 3. Phospholipid bilayers 4. Cellular buffering |
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what method is primarily used for measuring phosphate?
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Photometric: phosphomolybdate
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What specimen specifications apply to phosphate measurement?
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same as for calcium.
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What is the ref range for phosphate?
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0.8-1.6 mMol
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What is Magnesium's main function?
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As an enzyme cofactor and activator.
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List three methods for Mg measurement:
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1. Photometric - dye binding
2. AAS, cofactor assays 3. Free Mg++ assays (electrode) |
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What's the ref range of Mg2+?
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0.65-1.05 mMol - just a little lower than phosphate's range.
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Name the 4 main hormones of Mineral Metabolism:
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1. PTH
2. Calcitonin 3. PTrProtein 4. Vitamin D |
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2 other names for Vit D:
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1. Cholecalciferol
2. Calcitriol |
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What processes occur in bone remodeling?
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1. Bone resorption controlled by osteoclasts/PTH
2. Bone formation controlled by osteoblasts/Calcitonin |
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How does PTH work?
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increases blood Calcium levels by stimulating bone resorption.
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Where is PTH produced?
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in Parathyroid glands (4 little curds at the base of the thyroid)
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How does PTH respond to:
-Decreased serum Ca2+ -Decreased free Mg2+ -Increased vit D |
-Decreased serum Ca2+: increase
-Decreased free Mg2+: increase -Increased vit D: decrease |
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How does PTH affect phosphate concentration in the body?
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It reduces Phosphate reclamation in the renal proximal tubules
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What is overall PTH effect on:
-Serum Ca2+ concentration? -Phosphate concentration? |
Ca2+: Increases
Phosphate: Decreases |
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Where is Vit D derived from?
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Cholesterol
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What regulates Vit D levels?
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-Parathyroid hormone
-Phosphate levels |
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What is the function of Vit D?
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To regulate and maintain body Calcium and Phosphate levels
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Most important source of Vit D is:
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Sunlight
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Where is Calcitonin produced?
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Parafollicular cells in the thyroid gland
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Calcitonin's action is:
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decreased osteoclastic function to decrease body calcium levels and build bone.
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What influences body Calcitonin levels most?
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Body ionized calcium levels
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What is PTHrP?
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Parathyroid hormone related protein
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Where is PTHrP produced?
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Lactating breast tissue, cancer, pregnancy, tumors.
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What are causes of Hypocalcemia?
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-Low Albumin levels
-Chronic renal failure -Decreased Vit D -Hypoparathyroidism -Malabsorption |
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What kinds of physical symptoms result from hypo-calcemia?
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Muscle spasms and increased neuromuscular excitability
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What kind of affect on hormone levels would hypo-calcemia have?
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It would increase PTH
It would decrease Calcitonin |
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What is the primary treatment for hypocalcemia?
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Vit D and calcium supplements
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What are 3 causes of Hyper-calcemia?
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1. Hyperparathyroidism
2. Malignancy 3. Diuretics |
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What types of physical symptoms result from hyper-calcemia?
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-Neuromuscular
-Cardiac |
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What are 3 key symptoms of hyperparathyroidism and hypercalcemia of malignancy?
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1. Nausea
2. Vomiting 3. depression/lethargy |
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What 3 pieces result from PTH metabolism?
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1. N-terminal peptide
2. C-terminal peptide 3. Mid-molecule |
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-Why msr C-terminal PTH?
-Why msr N-terminal PTH? |
C: to monitor ongoing changes in disease
N: to monitor therapy response |
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What's detected in a C-term assay for PTH?
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-Mid-molecule PTH
-C-terminal PTH Therfore, secreted PTH and the C-terminal fragment. |
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What's detected in an N-term assay for PTH?
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-N-term fragments
-Newly secreted PTH |
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What's detected in an Intact PTH assay?
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only intact PTH
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How does Intact PTH assay only detect intact?
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-By using 2 antibodies.
-No C fragment b/c that would only bind 1 antibody. -No N fragment for same reason -PTHrP binds neither Ab. |
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Most common cause of primary hyperparathyroidism is?
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Benign parathyroid tumors; rarely caused by cancer.
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Most common cause of 2ndary hyperparathyroidism is?
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Chronic Renal Failure
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Why does CRF cause hyperparathyroidism?
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Kidneys can't excrete phosphate, so serum calcium levels drop to compensate for high serum phosphate; PTH senses the drop, increases to elevate the serum Ca2+.
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What other measurement is useful for evaluating PTH?
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Nephrogenic cAMP
|
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How is nephrogenic cAMP measured?
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-By radioimmunoassay
-Correction for filtration |
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What exactly does the nephrogenic cAMP assay detect?
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All bioavailable PTH (including PTHrP)
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What causes hypophosphatemia from intracellular shift?
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-Glucose IV
-Insulin -Respiratory alkalosis |
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What can cause hyperphosphatemia?
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-Renal failure (no excretion)
-Laxatives, enema, hemolysis -Cell death -Acidosis |