3. Calcium, Phosphorus, Magnesium
Terms
undefined, object
copy deck
- 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
3. Coagulation
4. MEmbrane potential
5. Enzyme cofactor - Calcium is measured in what forms?
-
1. Total
2. Free - What are 2 methods for total Ca measurement?
-
-Photometric
-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
Remove Mg
-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 calcium?
-Ionized calcium? -
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
2. ATP/NADP
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
2. Calcitonin
3. PTrProtein
4. Vitamin D - 2 other names for Vit D:
-
1. Cholecalciferol
2. Calcitriol - 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?
-Phosphate concentration? -
Ca2+: Increases
Phosphate: Decreases - Where is Vit D derived from?
- Cholesterol
- What regulates Vit D levels?
-
-Parathyroid hormone
-Phosphate levels - What is the function of Vit D?
- To regulate and maintain body Calcium and Phosphate levels
- Most important source of Vit D is:
- Sunlight
- 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
-Hypoparathyroidism
-Malabsorption - 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
2. Malignancy
3. Diuretics - What types of physical symptoms result from hyper-calcemia?
-
-Neuromuscular
-Cardiac - What are 3 key symptoms of hyperparathyroidism and hypercalcemia of malignancy?
-
1. Nausea
2. Vomiting
3. depression/lethargy - What 3 pieces result from PTH metabolism?
-
1. N-terminal peptide
2. C-terminal peptide
3. Mid-molecule -
-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
-C-terminal 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
-Insulin
-Respiratory alkalosis - What can cause hyperphosphatemia?
-
-Renal failure (no excretion)
-Laxatives, enema, hemolysis
-Cell death
-Acidosis