Calcium, Phosphorus, Trace Minerals
The reference method for magnesium is A. atomic absorption. B. flame spectrophotometry. C. calmagite. D. EDTA titration.
A. atomic absorption.
Which of the following constituents normally present in serum must be chemically eliminated so that it will not interfere with the measurement of serum magnesium? A. calcium B. chloride C. iron D. potassium
A. calcium Because calcium and magnesium are chemically similar, they tend to cross-react/interfere in methods used to analyze them. "Calcium shelters" prevent calcium interference in magnesium assays.
A hospitalized patient is experiencing increased neuromuscular irritability (tetany). Which of the following tests should be ordered immediately? A. calcium B. phosphorus C. BUN D. glucose
A. calcium Calcium (and magnesium) are tests that would be ordered to evaluate a possible cause of increased neuromuscular irritability/cramping, tremors, tetany, etc.
The deficiency of which of the following metals can cause a deficiency of iron? A. copper B. chromium C. cobalt D. zinc
A. copper Copper deficiency leads to decreased ceruloplasmin synthesis. Ceruloplasmin is a ferroxidase, involved in oxidizing ferrous iron to ferric iron as it is transferred from ferritin to transferrin, and into circulation to areas needing iron. A deficiency of copper can lead to a microcytic, hypochromic anemia with iron-deficiency characteristics.
The most frequent cause of hypermagnesemia is due to A. increased intake. B. hypoaldosteronism. C. acidosis. D. renal failure.
A. increased intake
A patient ha the following results serum iron: 250ug/dl (60-150ug/dl) TIBC: 350ug/dl (300-350ug/dl) The best conclusion based on these values is that this patient has A. iron hemachromatosis. B. chronic disease. C. iron deficiency anemia. D. normal iron status.
A. iron hemachromatosis The serum iron is elevated, and the TIBC is at the top of the reference range. Calculating the % saturation: (250/350) x 100 = 71%, so it is also elevated. Of the responses given, only response "a" would have lab values similar to these. The patient does not have normal iron status, and chronic disease and iron deficiency both cause decreased iron levels.
The following laboratory results are obtained on a 60-year-old woman who is complaining of anorexia, constipation, abdominal pain, nausea and vomiting: serum ionized calcium elevated serum phosphorus decreased urine calcium elevated urine phosphorus elevated What do these results suggest? A. primary hyperparathyroidism B. vitamin D deficiency C. hypoparathyroidism D. Paget's disease
A. primary hyperparathyroidism The serum ionized calcium is elevated, and the main causes of elevated calcium are primary hyperparathyroidism and/or hypercalcemia of malignancy. Paget's disease has no effect on calcium levels, so that can be ruled out. Both vitamin D deficiency and hypoparathyroidism would cause a decrease in serum calcium. The only choice left is primary hyperparathyroidsim, which is correct.
Which of the following is the most accurate measurement of phosphorus in serum? A. rate of phosphomolydate formation @ 340 nm B. measurement of phosphomolybdenum blue @ 680 nm C. formation of a complex with malachite green D. formation of a chromogen with alkaline picrate
A. rate of phosphomolydate formation @ 340 nm Phosphorus can be assayed by following the rate of phosphomolydate formation @340 nm: PO4 + ammonium molybdate --- [H+] ---> phosphomolybdate A second coupled reaction, reduction of phosphomolybdate to form phosphobolybdenum blue is colorimetric. Final absorbance is measured @660 nm. Alkaline picrate is used in analysis of creatinine.
Which of the processes below occurs when iron is in the oxidized (Fe+3) state? A. absorption by intestinal epithelium B. binding to transferrin and incorporation into ferritin C. reaction with chromogens in colorimetric assays D. None of the above is true.
B. binding to transferrin and incorporation into ferritin Ferritin binds the ferrous ion, but the ferrous ion is oxidized to the ferric ion by a ferroxidase prior to being put onto transferrin.
Which of the following conditions will cause erroneous ionized calcium results? Assume that the samples are collected and stored anaerobically, kept at 4°C until measurement, and stored for no longer than 1 hour. A. slight hemolysis B. blood collected in sodium oxalate C. collection in a barrier gel tube D. whole blood analysis of heparinized sample
B. blood collected in sodium oxalate Blood collected in tubes containing sodium oxalate will cause erroneous results. Oxalate will chelate the calcium and lead to falsely decreased values.
A reciprocal relationship exists between A. sodium and potassium. B. calcium and phosphorus. C. sodium and chloride. D. calcium and magnesium.
B. calcium and phosphorus.
Total iron-binding capacity is elevated if A. chronic infection is present. B. chronic iron deficiency is present. C. chronic iron overload is present. D. ferritin is increased.
B. chronic iron deficiency is present. In chronic iron deficiency, the serum iron is low, and the % saturation is low as well. Transferrin levels increase in iron deficiency, which increases the TIBC, and decreases the % saturation even more. In chronic infection/inflammatory conditions, transferrin decreases because it is a negative acute phase reactant. In chronic iron overload, all sites are saturated, and total iron binding capacity is very low. Transferrin, not ferritin, is most of what is measured to assess iron binding capacity.
Parathyroid hormone (PTH) secretion is stimulated by A. increased plasma Ca+2. B. decreased plasma Ca+2. C. decreased plasma Pi. D. increased Ca+2 absorption from the intestine.
B. decreased plasma Ca+2. Synthesis and secretion of PTH by the parathyroid gland is stimulated within a few minutes by a decrease in ionized calcium.
Calcitonin has a great effect on the fetus and young child and may be responsible for A. increases in plasma Ca+2 B. decreases in plasma Ca+2 C. increases in Ca+2 reabsorption in the renal tubule. D. increases in hydroxylation of 25-OH-Vitamin D.
B. decreases in plasma Ca+2 Calcitonin is considered to be a PTH antagonist, with its main action being to reduce blood calcium. It acts on bone and kidney; it inhibits/suppresses osteoclast bone resorption and enhances renal excretion of phosphate (as well as sodium, potassium and magnesium).
The trace element that appears to be associated with enhanced bone formation is A. iron. B. fluoride. C. copper. D. manganese.
B. fluoride. Fluoride can be incorporated into bone crystal, and increases bone mass. Administration of vitamin D with cyclic administration of fluoride may enhance bone formation.
PTH (parathyroid hormone) A. inhibits renal reabsorption of Ca+2 B. inhibits renal reabsorption of Pi C. inhibits Ca+2 mobilization from bone to plasma. D. inhibits Pi mobilization from bone to plasma.
B. inhibits renal reabsorption of Pi PTH stimulates osteoclasts (increases bone resorption), enhances renal tubular reabsorption of calcium, inhibits renal tubular reabsorption of phosphate, and stimulates renal production of active vitamin D.
Which of the following laboratory results is consistent with primary hypoparathyroidism? A. low calcium, low phosphorus B. low calcium, high phosphorus C. high calcium, low phosphorus D. high calcium, high phosphorus
B. low calcium, high phosphorus Decreased PTH would lead to decreased serum calcium, increased serum phosphorus (due to decreased renal excretion), and decreased active vitamin D production.
Which of the following reagents is used in a colorimetric method to quantitate the concentration of serum calcium? A. magon dye B. ortho-cresolphthalein C. malachite green D. molybdate
B. ortho-cresolphthalein Magon dye is used to quantitate magnesium, molybdate is used to quantitate phosphorus. ortho-cresolphthalein is used to quantitate calcium. Beta -hydroxyquinilone is added to prevent interference from other cations, especially magnesium.
The regulation of calcium and phosphorus metabolism is accomplished by which of the following glands? A. thyroid B. parathyroid C. adrenal D. pituitary
B. parathyroid
A patient's serum phosphorus level is found to be elevated but the physician cannot determine a physiological basis for this abnormal result. What could have caused an erroneous result to be reported? A. patient not fasting when blood was drawn B. specimen was hemolyzed C. diurnal variation D. patient is receiving IV glucose therapy
B. specimen was hemolyzed Hemolysis will cause phosphorus to be falsely increased. Elevated abnormal serum proteins may also cause interference in phosphorus assays, and may cause a false increase (or decrease in phosphorus, depending on the assay). Phosphorus levels decrease following meals, IV glucose or fructose therapy and with the menstrual cycle.
Total iron-binding capacity measures the serum iron transporting capacity and is an indirect measure of the concentration of A. hemoglobin. B. transferrin. C. haptoglobin. D. ferritin.
B. transferrin. TIBC ug/mL = TRANSFERRIN mg/dL x 1.25 Measuring transferrin, and calculating the TIBC underestimates the TIBC because iron is also bound to other proteins. The difference is considered to be clinically insignificant.
Which percentage of total serum calcium is nondiffusible/protein bound? A. 80-90% B. 51-60% C. 40-50% D. 10-30%
C. 40-50% About 45% of total serum calcium is protein bound, and is considered to be non-diffusible. About 45% is free, or "ionized" calcium, and about 10% is calcium complexed with citrate, phosphate, sulfate, lactate, etc., and together make up the diffusible calcium fraction.
Which of the statements below regarding iron metabolism is correct? A. The dietary requirement for adult men is about 1-2 mg/day. B. Normally 40-50% of ingested iron is absorbed. C. The daily requirement is higher for pregnant and menstruating females. D. Absorption increases with the amount of iron in the body stores.
C. The daily requirement is higher for pregnant and menstruating females. An adult male needs to absorb 1-2 mg/day of iron from the GI tract to compensate for the loss of 1-2 mg of iron per day. Since only about 10% of dietary iron is absorbed, an adult male would need to provide about 9 times the loss. Because females lose about 40-80 mLs of blood with each menstrual cycle (which is equivalent to about 20-40 mg of iron), they require more dietary iron. Pregnancy causes a loss of about 600- 900 mg of iron. Iron absorption increases with the body's need for iron.
Which statement about iron is NOT true? A. TIBC may be calculated from the transferrin concentration. B. Myoglobin has a higher affinity for iron that hemoglobin. C. Transferrin in serum is typically 99% saturated with iron. D. Serum iron is typically higher in males than females.
C. Transferrin in serum is typically 99% saturated with iron. Normal iron saturation is between 20-55%, and varies with age and sex. An iron saturation of 99% would be considered "iron overload"
Secondary hyperparathyroidism is often the result of A. vitamin C deficiency. B. liver disease. C. renal disease. D. pancreatic disease. E. thyroid disease
C. renal disease. In secondary hyperparathyroidsm, the parathyroid glands are okay, but the target tissues are not responding correctly. Renal disease can be a cause of secondary hyperparathyroidism because diseased kidneys do not respond to PTH appropriately. Calcium is lost in the urine, and the resulting hypocalcemia causes an increase in PTH.
Serum and urine copper levels are assayed on a hospital patient with the following results Serum Cu 58 ug/dL (70-140) Urine Cu 83 ug/dL (<40) This is most consistent with A. normal copper levels. B. Wilms' tumor. C. Wilson's disease. D. Addison's disease.
C. Wilson's disease. Wilson's disease is associated with copper accumulation in the body, including the liver, brain, kidney and cornea. Copper is transported normally from the intestines to the liver, but NOT from the liver into the bile. Less ceruloplasmin in made, less ceruloplasmin is in the plasma, so copper levels are low. Patients develop copper overload in the liver and the brain. The hallmarks of Wilson's disease are decreased serum copper, decreased ceruloplasmin, and increased urine copper. Sometimes Kayser-Fleischer rings (copper deposits in the cornea around the iris) may be seen using a special "slit lamp" for visualization. Treatment includes copper chelaters to increase urinary copper excretion, and zinc administration to decrease copper absorption in the gut. (Zinc competes with copper for absorption in the gut.)
Menkes' syndrome is caused by an accumulation in the intestinal mucosal cells and associated low plasma concentrations of A. iron. B. zinc. C. copper. D. manganese.
C. copper. Menke's syndrome is a recessive X-linked genetic defect in copper transport and storage. Copper is absorbed normally into intestinal mucosal cells, but defective transport out of mucosal cells results in copper deficiency. Symptoms include mental deterioration, failure to thrive, decreased activity of copper-containing enzymes, connective tissue abnormalities, "kinky" hair, and early death. Treatment includes administration of copper-histidine.
Iron is physiogically active, only in the ferrous form, in A. cytochromes. B. ferritin. C. hemoglobin. D. transferrin.
C. hemoglobin. Iron must be in the ferrous state to be able to bind oxygen. Hemoglobin with iron in the ferric state is called "methemoglobin", and is unable to bind oxygen. Iron cycles reversibly back and forth between the ferrous and ferric state in the cytochromes as ATP is generated. Ferritin binds the ferrous ion, but the ferrous ion is oxidized to the ferric ion by a ferroxidase prior to being put onto transferrin.
Which condition is associated with the lowest percent saturation of transferrin? A. hemochromatosis B. anemia of chronic infection C. iron deficiency anemia D. hemolytic anemia
C. iron deficiency anemia Hemochromatosis and hemolytic anemias will increase the % saturation of iron. Iron levels decrease in both iron deficiency anemia and anemia of chronic disease, but in iron deficiency anemia (IDA), you can severely deplete your iron. Transferrin levels increase in IDA, which only decreases the % saturation more. Anemia of chronic disease (AOCD) causes increased hepcidin production by the liver. As hepcidin increases, less iron is allowed out of cells and put on transferrin, so iron levels decrease. Transferrin is a negative APR, so transferrin levels also decline with inflammation. Even though iron levels decrease relatively more than transferrin levels in AOCD, and the % saturation drops to low levels, it is not as low as those seen in IDA.
Which of the following conditions is associated with an increase in ionized calcium in the blood? A. alkalosis B. hypoparathyroidism C. malignancy D. hyperalbuminemia
C. malignancy Alkalosis and hypoparathyroidism would cause a decrease in ionized calcium. Hyperalbuminemia would increase the total calcium levels, but it has no effect on ionized levels. The two most common causes of hypercalcemia are primary hyperparathyroidism and calcemia of malignancy.
Fasting serum phosphorus concentration is controlled primarily by the A. pancreas. B. skeleton. C. parathyroid gland. D. small intestine.
C. parathyroid gland. The small intestine would not be involved in fasting levels of phosphorus. Poor renal function also affects phosphorus.
If neonatal plasma Ca+2 is less than 7 mg/dL, it may indicate hypofunction of the A. pancreas. B. lungs. C. parathyroid gland. D. liver.
C. parathyroid gland. While transient hypocalcemia is not uncommon in neonates, especially preterm infants, it must be monitored to be sure that the parathyroid glands are functioning. Congenital hypoparathyroidism will cause hypocalcemia that does not resolve on its own within a few days after birth.
A low concentration of serum phosphorus is commonly seen in A. chronic renal disease. B. patients with pituitary tumors. C. patients being treated for DKA. D. hypothyroidism.
C. patients being treated for DKA. DKA is due to primary insulin deficiency. Once insulin is administered, glucose entry into cells leads to increased glycolosis, using phosphorus in the conversion of glucose to glucose-6-phosphate (the first step of glycolysis).
The following laboratory results were obtained Serum: Ca increased, PO4 decreased, ALP normal Urine: Ca increased, PO4 increased These results are most compatible with A. multiple myeloma. B. milk-alkali syndrome C. primary hyperparathyroidism. D. primary hypothyroidism.
C. primary hyperparathyroidism. Multiple myeloma patients tend to have elevated ALP levels due to the bone involvement of the plasma cell tumors. Milk-alkali syndrome, caused by ingestion of milk/cream and bicarbonate salts, is frequently associated with renal disease. There is decreased renal clearance of calcium and phosphorus, causing increased serum calcium and phosphorus. Primary hypothyroidism does not affect calcium or phosphorus levels.
Magnesium carbonate is added to an iron-binding capacity determination in order to A. allow color to develop. B. precipitate protein. C. remove excess unbound iron. D. bind with Hgb iron.
C. remove excess unbound iron.
Which of the following compounds is considered to be the "active" form of vitamin D? A. ergocalciferol B. cholecalciferol C. 25-hydroxy-vitamin D D. 1,25-dihyroxy-vitamin D
D. 1,25-dihyroxy-vitamin D Ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) are dietary sources of precursors for vitamin D. Dietary cholesterol can be converted to 7-dehydrocholesterol by small intestine mucosal cells, which can then be converted to cholecalciferol by UV light on the skin. The liver converts both ergocalciferol and cholecalciferol to 25-hydroxy-vitamin D. This form of vitamin D is the substrate for "active vitamin D", and is used as a marker for vitamin D nutritional status. PTHstimulates a kidney enzyme (1-hydroxylase) to produce 1,25-dihydroxy-vitamin D...the active form of vitamin D. Many tissues also have 1-hydroxylase activity, producing active vitamin D when needed by the cells.
A serum ferritin level may not be a useful indicator of iron deficiency anemia in patients with what type of disorder? A. chronic infection B. malignancy C. viral hepatitis D. All of the above are correct.
D. All of the above are correct. A large number of chronic diseases result in an increased serum ferritin concentration. These diseases include chronic infections, chronic inflammatory disorders, renal disease, heart disease, and numerous malignancies (especially lymphomas, leukemias and breast cancers). An increase in plasma ferritin levels occurs in cases of viral hepatitis or toxic liver injury as a result of release of ferritin from the damaged liver cells.
__________ is an iron storage protein in the RE system. A. Transferrin B. Cytochrome C. Peroxidase D. Ferritin
D. Ferritin
Plasma calcium levels may be influenced by all of the following EXCEPT A. parathyroid hormone. B. vitamin D. C. calcitonin. D. aldosterone.
D. aldosterone. Aldosterone affects sodium, potassium and even hydrogen ions in some situations, but not calcium.
Which of the following calcium methodologies utilizes lanthanum chloride to eliminate interfering substances? A. ortho-cresolphthalein B. ion-selective electrode C. chelation with EDTA D. atomic absorption spectrophotometry
D. atomic absorption spectrophotometry Did you get the GOOGLE question? =D Phosphate, sulfate and aluminum interfere in the atomic absorption method for calcium, but are masked by the addition of lanthanum chloride. To prepare the lanthanum chloride: Dissolve 29 grams of La203 in 250 mL of concentrated HCl. (CAUTION: reaction is violent!) Dilute to 500 mL with deionized water. Add 2 mLs of lanthanum chloride solution to 20 mL of sample before analysis. Magnesium levels > 10 mg/dL cause falsely decreased levels of calcium. Sodium and potassium do not interfere.
Ninety percent of the copper present in the blood is bound to A. transferrin. B. haptoglobin. C. albumin. D. ceruloplasmin.
D. ceruloplasmin. Okay, technically 90% copper is not "bound" to ceruloplasmin...more like "incorporated" into it. There is a small amount of copper that circulates around on albumin and transcuprein
Which of the following test results is a specific marker for osteoporosis? A. high urinary calcium B. high serum phosphorus C. low parathyroid hormone D. high urinary alpha-2N-telopeptide
D. high urinary alpha-2N-telopeptide Bone resorption by osteoclasts results in the production of cross-linked N-telopeptides of type I collagen (NTx). NTx is specific to bone and is found in the urine as a stable end product of bone degradation. The levels of NTx correlate with the rate of bone resorption (increased levels are seen with increased bone resorption). It is used to predict and monitor skeletal response to hormonal antiresorptive therapy for osteoporosis and/or Paget's disease.
Which of the following is an effect of increased parathyroid hormone secretion? A. decreased blood calcium levels B. increased renal reabsorption of phosphorus C. decreased bone reabsorption D. increased intestinal absorption of calcium
D. increased intestinal absorption of calcium PTH increases in an attempt to increase plasma ionized calcium. Its actions include stimulation of osteoclasts so that bone is reabsorbed, and enhances absorbtion of calcium from the gut and renal tubules. Phosphorus reabsorption is decreased.
Which of the following is most likely to be ordered in addition to serum calcium to determine the cause of tetany? A. vitamin D B. sodium C. phosphorus D. magnesium
D. magnesium Both calcium and magnesium are involved in proper neuromuscular activity.
Increased serum iron and increased total iron binding capacity (TIBC) may be seen in A. chronic infection, malignancies. B. iron deficiency anemia. C. acute blood loss, obstructive jaundice. D. pernicious anemia, chronic iron poisoning. E. All of the above are correct.
D. pernicious anemia, chronic iron poisoning. This is one of those "choose the best answer" kind of questions. The question asks about INCREASED serum iron and INCREASED TIBC, so start with the increased iron, and consider which of the responses would demonstrate increased iron. Of the choices, only response "d" (pernicious anemia, chronic iron poisoning) would have increased serum iron. That's the answer!
In colorimetric methods for determining inorganic phosphate, molybdenum blue is formed by __________ which act on phosphomolybdate. A. oxidizing agents B. stabilizing agents C. defoaming agents D. reducing agents
D. reducing agents PO4 + ammonium molybdate ---[acid pH]---> phosphomolybdate phosphomolybdate ---[reducing agent]---> molybdenum blue Phosphomolybdate absorbs at 340 nm, and when reduced forms molybdenum blue, which absorbs at 660 nm.
Which of the following conditions is associated with hypophosphatemia? A. hypervitaminosis D B. renal failure C. multiple myeloma D. rickets
D. rickets Rickets is caused by a vitamin D deficiency. Calcium and phosphorus absorption in the gut is diminished, leading to decreased serum levels. Hypervitaminosis D (excess vitamin D), renal failure and multiple myeloma with bone involvement, will all cause hyperphosphatemia.
A patient's blood was drawn at 0800 for a serum iron determination. The result was 85 ug/dL. A repeat specimen was collected at 2000; the serum was stored at 4°C and run the next morning. The result was 40 ug/dL. These results are most likely due to A. iron deficiency anemia. B. improper storage of the specimen. C. possible liver damage. D. the time of day the specimen was drawn.
D. the time of day the specimen was drawn. Iron demonstrates diurnal variation, with levels higher in the morning and lower in the evening.
Low Ca+2 and low Pi in plasma and symptoms of rickets may indicate A.hyperparathyroidism. B. hypothyroidism. C. decreased calcitonin secretion. D. vitamin D deficiency.
D. vitamin D deficiency. Rickets are bone changes in children characteristic of vitamin D deficiciency. The growing skeleton is involved and defective mineralization occurs in the spiphysial cartilages and bone. The long bones cannot withstand normal mechanical stresses and tend to bend, or "bow". Frequent fractures occur.
What metal may be used as a treatment for Wilson's disease? A. copper B. molybdenum C. fluorine D. zinc
D. zinc Zinc competes with copper for absorption in the gut, and causes less copper to be absorbed.
The deficiency of what trace metal is associated with growth retardation, dermatitis, reduced taste acuity, and impaired wound healing? A. copper B. iron C. selenium D. zinc
D. zinc Zinc deficiency is also associated with diarrhea, impotence, sensory alterations, decreased T-cell function and increased susceptibility to infections. Copper deficiency may cause a microcytic, hypochromic anemia and neutropenia. Iron deficiency may cause a microcytic, hypochromic anemia. Selenium deficiency is associated with cardiomyopathy, skeletal muscle weakness, osteoarthritis and increased incidence of cancer.
which pattern most likely represents iron deficiency a. Ferritin decreased, transferrin increased, serum iron increased b. Ferritin increased, transferrin increased, serum iron increased c. Ferritin decreased, transferrin increased, serum iron decreased d. Ferritin decreased, transferrin decreased, serum iron decreased
c. Ferritin decreased, transferrin increased, serum iron decreased Iron deficiency means inadequate iron, so only responses "c" or "d" could be proper choices. Both responses have decreased ferritin, so the question comes down to this: In iron deficiency anemia, is the transferrin increased or decreased? Transferrin is increased in iron deficiency anemia, increasing the TIBC, and decreasing the % saturation.
