Deck 39: Disorders of Bone and Mineral Metabolism

Question 1

An individual's serum phosphate level is decreased but his physician cannot determine a physiological basis for this abnormal result.What could possibly have caused this result?

A) Individual not fasting when blood was drawn
B) Specimen hemolysis
C) Use of IV carbohydrate therapy to stimulate insulin secretion
D) Diurnal variation

Answer 1

Use of IV carbohydrate therapy to stimulate insulin secretion

Question 2

In a case of osteomalacia related to vitamin D deficiency,would serum calcium be increased,decreased,or remain unchanged?

A) Increased
B) Decreased
C) Remain unchanged

Answer 2

Decreased

Question 3

The major cause of the decrease in total bone mass in an aging osteoporotic woman is:

A) being postmenopausal and estrogen deficient.
B) lack of vitamin D.
C) severe hypocalcemia.
D) increased PTH.

Answer 3

being postmenopausal and estrogen deficient.

Question 4

Magnesium:

A) concentration is present mostly in the complexed state.
B) decrease produces neuromuscular excitability.
C) is the second most abundant intracellular cation.
D) concentration is decreased with excessive intake of antacids.

Question 5

Hypoparathyroidism is most commonly caused by:

A) resistance to parathyroid hormone.
B) adenoma of the parathyroid gland.
C) pseudohypoparathyroidism.
D) parathyroid gland destruction.

Question 6

The clinical usefulness of calcitonin measurement is:

A) in the assessment of primary hyperparathyroidism.
B) in the determination of sources of vitamin D deficiency.
C) the differential diagnosis of multiple endocrine neoplasia (MEN).
D) as a tumor marker for medullary thyroid carcinoma.

Question 7

Which one of the following analytes is most useful in distinguishing primary from secondary hyperparathyroidism?

A) Parathyroid hormone
B) Serum calcium
C) Vitamin D
D) Serum phosphorus

Question 8

An individual has the following laboratory test results: increased serum calcium,decreased serum phosphorus,increased parathyroid hormone.This individual most likely has:

A) hyperparathyroidism.
B) hypoparathyroidism.
C) hyperthyroidism.
D) renal failure.

Question 9

A noncollagenous protein marker of bone formation that is released from bone during bone resorption,regulated by 1,25-dihydroxyvitamin D,and synthesized by osteoblasts and that regulates insulin secretion and sensitivity is:

A) n-telopeptide.
B) deoxypyridinoline.
C) hydroxyproline.
D) osteocalcin.

Question 10

Telopeptides:

A) are released from type I collagen during bone resorption.
B) are enzymes that become elevated during bone growth.
C) are proteins found in bone whose serum level can reflect bone formation.
D) is the most abundant noncollagenous protein in bone.

Question 11

Rickets is sometimes associated with deficiency of which one of the following vitamins?

A) B₁₂
B) A
C) D
D) C

Question 12

Hypercalcemia occurs in humoral hypercalcemia of malignancy (HHM)because:

A) tumors synthesize parathyroid hormone (PTH),which increases calcium levels in blood.
B) metastasizing cells synthesize calcium and release it into the circulation.
C) PTH-related protein (PTHrP)is synthesized by tumors and stimulates bone resorption.
D) osteoclasts bind tumor marker proteins and the process of bone remodeling becomes unregulated.

Question 13

Hypophosphatemia is seen in all of the following except:

A) intravenous glucose administration.
B) vitamin D deficiency.
C) hyperparathyroidism.
D) malabsorption.

Question 14

In a case of severe osteomalacia,would bone-specific alkaline phosphatase be increased,decreased,or remain unchanged?

A) Increased
B) Decreased
C) Remain unchanged

Question 15

In bone:

A) calcium is complexed with bicarbonate.
B) the collagen component is type II collagen.
C) osteoclasts are responsible for bone formation.
D) osteoblasts are the bone-forming cells.

Question 16

A blood specimen is collected in a heparin-containing tube for calcium and magnesium determination.Upon centrifugation,the plasma appeared hemolyzed.How would this affect the magnesium value?

A) There would be no effect on the magnesium value.
B) The magnesium would form complexes with the hemoglobin and the results would indicate a false negative value.
C) The magnesium would be incorporated into the bilirubin molecule,leading to a false negative value.
D) Because erythrocytes contain magnesium,hemolysis would increase its apparent value.

Question 17

Total serum calcium:

A) consists of an equal mix of free and protein-bound calcium.
B) contains a 10% fraction that is complexed to small anions.
C) is 80% bound to albumin.
D) contains a 25% fraction that is free and unbound.

Question 18

Which one of the following diseases is characterized by a loss in bone mass?

A) Osteoporosis
B) Osteomalacia
C) Rickets
D) Bone cancer

Question 19

The primary physiological regulator of parathyroid hormone (PTH)synthesis and secretion is:

A) PTH releasing hormone from the pituitary gland.
B) the concentration of free calcium in blood or extracellular fluid.
C) the concentration of PTH in blood.
D) PTH stimulating hormone.

Question 20

What makes up the organic matrix component of bone?

A) Calcium,protein,and collagen
B) Cells and collagen only
C) Minerals and cells only
D) Cells only

Question 21

Specimen requirements for assessing free calcium using ion-selective electrode methodology include:

A) heparinized whole blood.
B) heparinized plasma.
C) serum.
D) all of the above.

Question 22

Which of the following is a recognized clinical feature of hypercalcemia?

A) Muscle tetany
B) Muscle weakness
C) Dementia
D) Mental retardation

Question 23

Pseudohypoparathyroidism is characterized by tissues that are resistant to the effects of circulating levels of parathyroid hormone (PTH).Which one of the following sets of values presents expected laboratory findings in this disorder?

A) Calcium,phosphorus,and PTH within healthy reference intervals
B) Elevated calcium,decreased phosphorus,normal PTH
C) Decreased calcium,elevated phosphorus,elevated PTH
D) Elevated calcium,elevated phosphorus,decreased PTH

Question 24

A factor that would alter protein binding of calcium and its redistribution among the three plasma pools would be:

A) a change in an individual's posture.
B) liver disease.
C) increased citrate concentration.
D) an altered anion gap.

Question 25

Hypermagnesia may be observed in all of the following except:

A) excessive intake of antacids.
B) gastrointestinal disorders.
C) administration of magnesium in the presence of renal disease.
D) enemas.