Bone Mineral Disorders (Pedia)

Question 1

What percentage of body calcium is rapidly exchangable?

Answer 1

1%

Question 2

What percentage of serum calcium is bound?

Answer 2

40% is bound to albumin
10% is bound to citrate, lactate, bicarbonate, phosphate, and sulfate
50% is biologically active

Question 3

What are the “second messengers” involved in calcium transport?

Answer 3

cAMP, inositol, 1,4,5-triphosphate, and diacylglycerol

Question 4

What is the molecular “pore” through which calcium enters the cell

Answer 4

alpha subunit

Question 5

What are the functions of serum ionized calcium modulator?

Answer 5

signal transduction, cell to cell adhesion, clotting, muscular contraction, cardiac rhythmicity, enzyme action, synthesis and secretion of endocrine factors, cellular proliferation

Question 6

How does the kidney contribute to the regulation of iCa?

Answer 6

transcellular reabsorption of calcium in the distal convoluted tubules

Question 7

What portion of the PTH molecule binds to receptors in target organs?

Answer 7

amino terminus

Question 8

What is the net effect of PTH?

Answer 8

1. increased serum calcium

2. decreased serum phosphorus

Question 9

What is the effect of calcitriol on intestinal absorption?

Answer 9

inc. absorption of calcium and phosphorus

Question 10

What is the net effect of calcitriol?

Answer 10

increased serum calcium and phosphorus

Question 11

Calcitonin is primarily secreted by?

Answer 11

parafollicular thyroid cells

Question 12

What portion of vitamin D synthesis occurs in the liver?

Answer 12

hydroxylation (product is calcidiol)

Question 13

Calcitonin is used as a marker for which type of malignancy?

Answer 13

medullary thyroid CA

Question 14

In hypocalcemia, what are the values of total serum and ionized Ca?

Answer 14

Total serum Ca < 7.5 mg/dL

Ionized Ca < 1.2 mmol/L

Question 15

What are the possible causes of pseudohypocalcemia?

Answer 15

hypoalbuminemia, alkalosis, elevated free fatty acids, lipid infusion, gadolinium contrast

Question 16

What is the Chvostek sign?

Answer 16

contraction of the orbicularis oris when the masseter muscle is tapped

Question 17

What is the Trosseau sign?

Answer 17

induced spasm when pressure is applied to the forearm

Question 18

What are the chronic Ssx of hypocalcemia?

Answer 18

calcification of basal ganglia, cataracts, rickets and osteomalacia

Question 19

What drugs can cause hypocalcemia?

Answer 19

biphosphanates, diuretics, citrate

Question 20

What are the causes of transient, abnormal PTH secretion?

Answer 20

hypomagnesemia, critical illness, pregnancy, toxicity

Question 21

What are the characteristic radiologic findings in hypocalcemic rickets?

Answer 21

widening and cupping of epiphyses, metaphyseal distortion from osteomalacia

Question 22

What are the 3 forms of hypocalcemic rickets?

Answer 22

nutritional deficiency, vitamin D-dependent, vitamin D-resistant

Question 23

What is pseudohypoparathyroidism?

Answer 23

resistance to PTH characterized by supranormal PTH levels

Question 24

What is the first-line treatment for hypocalcemia?

Answer 24

10% calcium gluconate (not over 2 ml/kg in 10 minutes)

Question 25

What are the maternal risk factors for neonatal hypocalcemia?

Answer 25

maternal diabetes mellitus and hyperparathyroidism, vitamin D or Mg deficiency

Question 26

What are the causes of hypercalcemia?

Answer 26

excessive PTH production, altered calcium sensing, excessive PTH receptor activity

Question 27

What are the treatments for severe hypercalcemia?

Answer 27

hydration, loop diuretics, hemodialysis, calcitonin, biphosphonates