Glossary of 3. Calcium, Phosphorus, Magnesium
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- Where is most of the body's calcium? Where is the least?
- Most = skeleton
Least = ionized
- What are 5 functions of Ca?
- 1. Muscle contraction
2. Bone mineralization
4. MEmbrane potential
5. Enzyme cofactor
- Calcium is measured in what forms?
- 1. Total
- What are 2 methods for total Ca measurement?
-Atomic absorption spectrometry
- Name 2 different photometric methods for calcium:
- 1. O-cresolphthalein complexone
2. Arsenazo III
- -What color does the O-cresolph complexone reaction produce?
-At what pH?
-What else has to be done?
- Red color
pH = 10-12
-Competes with 8-hydroxyquinolone.
- 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.
- What method is used to measure ionized calcium?
- Ion-selective electrode.
- What is the reference range of:
- Total: 2.2-2.6 mmol/L
Ionized: 1.0-1.2 mmol/L
- What specimens can be used for calcium measurements?
- Serum or heparin whole blood
- What can't be used?
- Citrate, oxalate, EDTA
- What should be done to specimens intended for Ca measurement?
- Remove RBCs right away to prevent Calcium uptake.
- What can alter calcium measurements horribly?
- Gross hemolysis.
- What physiologic measurement needs to be minded in Ca msmt?
- pH; acid pH means more H+ will be on albumin, displacing Ca and increasing the free Ca+ measurement. Vice versa.
- Name four functions of phosphate:
- 1. Hydroxyapetite
3. Phospholipid bilayers
4. Cellular buffering
- what method is primarily used for measuring phosphate?
- Photometric: phosphomolybdate
- What specimen specifications apply to phosphate measurement?
- same as for calcium.
- What is the ref range for phosphate?
- 0.8-1.6 mMol
- What is Magnesium's main function?
- As an enzyme cofactor and activator.
- List three methods for Mg measurement:
- 1. Photometric - dye binding
2. AAS, cofactor assays
3. Free Mg++ assays (electrode)
- What's the ref range of Mg2+?
- 0.65-1.05 mMol - just a little lower than phosphate's range.
- Name the 4 main hormones of Mineral Metabolism:
- 1. PTH
4. Vitamin D
- 2 other names for Vit D:
- 1. Cholecalciferol
- What processes occur in bone remodeling?
- 1. Bone resorption controlled by osteoclasts/PTH
2. Bone formation controlled by osteoblasts/Calcitonin
- How does PTH work?
- increases blood Calcium levels by stimulating bone resorption.
- Where is PTH produced?
- in Parathyroid glands (4 little curds at the base of the thyroid)
- 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
- How does PTH affect phosphate concentration in the body?
- It reduces Phosphate reclamation in the renal proximal tubules
- What is overall PTH effect on:
-Serum Ca2+ concentration?
- Ca2+: Increases
- Where is Vit D derived from?
- What regulates Vit D levels?
- -Parathyroid hormone
- What is the function of Vit D?
- To regulate and maintain body Calcium and Phosphate levels
- Most important source of Vit D is:
- Where is Calcitonin produced?
- Parafollicular cells in the thyroid gland
- Calcitonin's action is:
- decreased osteoclastic function to decrease body calcium levels and build bone.
- What influences body Calcitonin levels most?
- Body ionized calcium levels
- What is PTHrP?
- Parathyroid hormone related protein
- Where is PTHrP produced?
- Lactating breast tissue, cancer, pregnancy, tumors.
- What are causes of Hypocalcemia?
- -Low Albumin levels
-Chronic renal failure
-Decreased Vit D
- What kinds of physical symptoms result from hypo-calcemia?
- Muscle spasms and increased neuromuscular excitability
- What kind of affect on hormone levels would hypo-calcemia have?
- It would increase PTH
It would decrease Calcitonin
- What is the primary treatment for hypocalcemia?
- Vit D and calcium supplements
- What are 3 causes of Hyper-calcemia?
- 1. Hyperparathyroidism
- What types of physical symptoms result from hyper-calcemia?
- What are 3 key symptoms of hyperparathyroidism and hypercalcemia of malignancy?
- 1. Nausea
- What 3 pieces result from PTH metabolism?
- 1. N-terminal peptide
2. C-terminal peptide
- -Why msr C-terminal PTH?
-Why msr N-terminal PTH?
- C: to monitor ongoing changes in disease
N: to monitor therapy response
- What's detected in a C-term assay for PTH?
- -Mid-molecule PTH
Therfore, secreted PTH and the C-terminal fragment.
- What's detected in an N-term assay for PTH?
- -N-term fragments
-Newly secreted PTH
- What's detected in an Intact PTH assay?
- only intact PTH
- How does Intact PTH assay only detect intact?
- -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.
- Most common cause of primary hyperparathyroidism is?
- Benign parathyroid tumors; rarely caused by cancer.
- Most common cause of 2ndary hyperparathyroidism is?
- Chronic Renal Failure
- Why does CRF cause hyperparathyroidism?
- 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+.
- What other measurement is useful for evaluating PTH?
- Nephrogenic cAMP
- How is nephrogenic cAMP measured?
- -By radioimmunoassay
-Correction for filtration
- What exactly does the nephrogenic cAMP assay detect?
- All bioavailable PTH (including PTHrP)
- What causes hypophosphatemia from intracellular shift?
- -Glucose IV
- What can cause hyperphosphatemia?
- -Renal failure (no excretion)
-Laxatives, enema, hemolysis
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