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endocrine - Ca and phosphate homeostasis Flashcards

0
Q

Bone cell type for production of matrix

A

Osteoblast

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1
Q

Circulating forms of calcium

A

Ionized - 50%
Protein-bound - 40%
Complexed with anion - 10%

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2
Q

Bone cell type for resorption of matrix

A

Osteoclasts

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3
Q

Hormones and minerals found in bones

A 
PTH
Vit D
Calcitonin
Calcium
Phosphorus
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4
Q

Predominant parenchymal cell type and a primary endocrine cell of parathyroid gland

A

Chief/principal cell

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5
Q

Larger, mitochondria-rich, eosinophilic cell type of parathyroid gland

A

Oxyphil cell

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6
Q

Major regulator of calcium and phosphorus metabolism

A

PTH

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7
Q

The most important effect of PTH is to increase/decrease plasma calcium level

A

Increase plasma calcium level

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8
Q

The most important effect of PTH is to increase plasma Ca level by

A

Stimulate bone resorption
Increase renal tubular reabsorption
Stimulate renal 1,25 dihydroxy- D synthesis

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9
Q

PTH decrease /increase plasma phosphate

A

Decrease plasma phosphate

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10
Q

PTH decrease plasma phosphate by

A

Inhibiting renal tubular phosphate reabsorption

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11
Q

Parathyroid cell type that secretes PTH

A

Chief cell

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12
Q

Primary target of PTH

A

Bone

Kidneys

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13
Q

PTH receptors

A

PTH1R (hPTH/PTHrP)
PTH2R
CPTH

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14
Q

Pty receptor that bonds both PTH and PTHrP

A

PTH1R

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15
Q

PTH receptor that activates adenylyl cyclase and PLC

A

PTH1R

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16
Q

PTH receptor that is abundant in bones (osteoblasts) and kidneys (prox and distal convoluted tubules)

A

PTH1R

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17
Q

PTH receptor that does not bind to PTHrP

A

PTH2R

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18
Q

PTH receptor that is found in brain, placenta and pancreas

A

PTH2R

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19
Q

PTH receptor that reacts with the carboxylate terminal rather than amino terminal of PTH

A

CPTH

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20
Q

Primary stimulating signal of PTH

A

Low circulating Ca level

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21
Q

Low circulating Ca level is sensed by principal cells thru

A

Ca-sensing receptor (CaSR)

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22
Q

High Mg level inhibits PTH

A

True

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23
Q

PTH stimulation

A 
Phosphodieasterase inhibitors 
Epinephrine
Dopamine
Histamine
Lithium
Thiazides diuretics
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24
PTH inhibition
A-adrenergic agonists Prostaglandins Aluminum Chromogranin
25
Mechanism of action of PTH in kidneys
Stimulates Ca reabsorption Inhibits Pi reabsorption Stimulates conversion to 1,25 dihydroxy vitamin D
26
Vit D3
Cholecalciferol
27
Vit D synthesis
7-dehydrocholesterol -(skin UV light)- cholecalciferol - (liver vitD 25-hydroxylase)- 25hydroxycholecalciferol -(kidney 1a-hydroxylase)- 1,25dihydroxyvitamin D
28
Rate limiting enzyme in vit d synthesis
1a-hydroxylase (CYP1a)
29
Secosteroid (class of steroid with 1 open cholesterol ring)
Vit D3
30
Ergocalciferol, secosteroid produced in plants. Enters the liver for hydroxylation via portal circulation and chylomicrons
Vit D2
31
Facilitates absorption of Ca in duodenum and jejunum
Vit d
32
Percentage of active vit d that circulates as free steroid
0.4%. | Other binds to DBP from liver
33
What kind of receptor is vit D receptor
Nuclear receptor
34
Low Ca stimulates renal 1a-hydroxylase thru increased PTH
High Ca inhibits 1a-hydroxylase thru CaSR in proximal tubule
35
Very active vit D preparation
Calcitriol
36
Effect of calcitonin to phosphate and Ca level
Decrease Ca and decrease phosphate
37
Effect of PTH to phosphate and Ca level
Increase Ca | Decrease phosphate
38
Effect of vitD to phosphate and Ca level
Increase Ca | Increase phosphate
39
Bone remodeling is regulated by
PTH
40
Calcitonin is produce by what cell
Parafollicular C cell
41
Calcitonin is regulated by
CaSR and high Ca level
42
Calcitonin is primarily inactivated in what organ
Kidney
43
Inhibits bone resorption
Calcitonin | As decreases Ca and Pi
44
Useful histo chemical marker for MEdullary thyroid Ca
Calcitonin
45
Calcitonin is expressed in
Osteoclast (inhibits bone resorption) | Nephrons (inhibits Ca and Pi reabsorption)
46
Major stimulus of calcitonin
Hypercalcemia
47
Normal calcitonin plasma level
10-20pg/mL Any increase In plasma Ca by 1mg/dl will result to 2-10fold acute rise in calcitonin
48
Calcitonin release is stimulated by
Vit D | Ingestion of food due to GASTRIN
49
Inhibitors of calcitonin
Low vit D | Somatostatin
50
Calcitonin excess does not produce hypocalcemia (MTC). | Calcitonin deficiency does not produce hypercalcemia (post total thyroidectomy for thyroid Ca )
Calcitonin plays a very minimal or negligible physiologic role in Ca and phosphate homeostasis
51
Hyperparathyroidism is an excessive production of PTH that is usually due to single adenoma. It has high/low Ca and high/low Pi.
High Ca and low Pi
52
High Ca and low Pi in hyperparathyroidism is due to
Bone demineralization High GI Ca absorption High renal Ca reabsorption
53
Hypoparathyroidism is due to PTH and vitD deficiency. It has high/low Ca and high/low Pi.
Low Ca and high Pi
54
The low Ca and high Pi in hypoparathyroidism is due to
Impaired GI Ca absorption Decreased renal reabsorption Decreased bone Ca mobilization
55
Bone is not affected in hypoparathyroidism
True
56
Rare familial disorder charac by tissue resistance to PTH.
Pseudo hypoparathyroidism
57
There is high PTH secretion, low Ca and congenital defects of skeleton.
Pseudo hyperparathyroidism
58
Mg and Ca in vit D deficiency
Low mg and Ca
59
VitD deficiency leads to defective bone mineralization in adults
Osteomalacia
60
VitD deficiency leads to defective bone mineralization in children
Rickets
61
VitD deficiency leads to secondary increase in PTH
Osteoporosis
62
Results in bone deformities due to increase bone resorption ff by increase bone formation. It has high alkaline phosphatase, osteocalcin and urinary hydroxyproline. It produces pain, bone deformation and bone weakness.
Paget's disease
63
As in chronic renal disease with high Pi and low Ca due to high PTH and low vit D
Renal osteodystrophy

Med Prep (52 decks)

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