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Endocrine Pharmacology > Agents Affecting Bone Mineral Homeostasis > Flashcards

Agents Affecting Bone Mineral Homeostasis Flashcards

1
Q

Drug List for Calcium Regulating Hormones Categories?

A 
A. Parathyroid hormone
B. Calcitonin
C. Vitamin D agents
D. Bisphosphonates
E. Calcium Sensing Receptor Mimetics (calcimimetics)
F. Various forms of calcium supplements
G. Fluoride
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2
Q

Parathyroid hormone Drugs?

A
  1. teriparatide, hPTH(1-34)

2. full length hPTH(1-84)

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3
Q

Calcitonin Drugs?

A
  1. Synthetic human calcitonin hCT

2. Natural calcitonin from salmon

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4
Q

Vitamin D agents

A
  1. cholecalciferol = Vitamin D3 (fish liver oils)
  2. ergosterol
  3. ergocalciferol (after irradiation) = Vitamin D2
  4. 25-OH cholecalciferol
  5. calcipotriol
  6. dihydrotachysterol (reduced Vitamin D2 , DHT)
  7. paricalcitol
  8. 22-oxacalcitriol
  9. calcitriol
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5
Q

Bisphosphonates agents?

A 
First Generation
1. etidronate 
Second Generation
2. alendronate 
3. pamidronate 
4. ibandronate 
Third Generation
5. risedronate  
6. tiludronate 
7. zoledronate
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6
Q

Calcium Sensing Receptor Mimetics (calcimimetics)

A

cinacalcet

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7
Q

Regulation of Calcium Homeostasis is controlled by 3 calcitropic hormones?

A

– Parathyroid hormone, PTH
– Calcitonin
– Calcitriol, the active form of Vitamin D
– Coordination of these 3 hormones controls the
concentration of Ca2+ in blood.

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8
Q

Pools of Calcium in the Body

A

Intracellular calcium: 100 nM to greater than 1 μM.
Calcium in blood and extracellular fluid: 1 mM.
Bone calcium: Vast majority of body calcium.

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9
Q

Plasma calcium is tightly regulated at:

A

2.5 mM = 5 mEq/L = 10 mg/dl

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10
Q

Components of Plasma Calcium:

A

– 40 % protein-bound (albumin)
– 10 % complexed (citrate, phosphate)
– 50 % diffusable, ionic calcium or “free
calcium” (Ca2+ = 1 mM)

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11
Q

Three major sites of action for blood calcium

regulation:

A

– Bone.
– Gastrointestinal tract.
– Kidney.

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12
Q

Bone. Calcium and phosphate in the blood are in

equilibrium with the?

A

Hydroxyapatite of bone. This allows resorption of bone calcium into blood.

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13
Q

Gastrointestinal tract. Total dietary intake of

calcium is?

A

About 1,000 mg per day. Excretion in feces is 900 mg per day.

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14
Q

Kidney. Excretion of calcium by the kidney is?

.

A

About 100 mg per day

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15
Q

Parathyroid Hormone (PTH) Functions to?

A

Increase plasma Ca2+

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16
Q

Parathyroid Hormone (PTH) is synthesized by and acts on?

A 
Synthesized by parathyroid glands
3 major actions:
– Increases bone resorption  Ca2+
– Increases kidney reabsorption  Ca2+
– Increases active form of Vitamin D
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17
Q

Calcium-Sensing Receptor are?

A

(G protein-coupled receptor)

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18
Q

Activation of the calcium sensor has two major signal-transducing effects:

A
  1. Activation of phospholipase C, which leads to generation of the second messengers diacylglycerol and inositol trisphosphate.
  2. Inhibition of adenylate cyclase, which suppresses intracellular concentration of cyclic AMP.
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19
Q

What allows both PTH- and Calcitoninsecreting cells to respond to extracellular calcium, and where is it found?

A

Calcium-Sensing Receptor (G protein-coupled receptor)

In both parathyroid glands and parafollicular cells of thyroid.

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20
Q

The calcium sensor is also expressed in?

A

Several cell types in the kidney, osteoblasts, a variety of hematopoietic cells in bone marrow, and in the
gastrointestinal mucosa.

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21
Q

Where is Calcitonin synthesized and what is its function and major actions?

A

Synthesized by parafolicular cells of thyroid and
Functions to decrease plasma Ca2+.
3 major actions:
– Decreases bone resorption
– Decreases kidney reabsorption
– Decreases active form of Vitamin D
In general, calcitonin opposes PTH actions.

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22
Q

Calcitonin also synthesized in other tissues?

A

Including the lung and intestinal tract.

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23
Q

Where is Calcitriol synthesized and what is its function?

A

The active form of Vitamin D and Functions to increase plasma Ca2+. Synthesized in skin and blood

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24
Q

Calcitriol most important physiological action?

A

Increases calcium uptake from GI

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25
Calcitriol additional pharmacological actions include?
Increases kidney reabsorption (pharmacologic dose) Increases bone resorption (pharmacologic dose) This is paradoxical, but true, and increasing doses promote even more resorption. Calcium can reverse this effect.
26
Things that can cause a loss of Calcium Homeostasis?
``` Estrogen deficiency (postmenopausal osteoporosis) Glucocorticoid excess Growth hormone deficiency Insulin deficiency Primary hypoparathyroidism Cancer ```
27
Low Calcium is detected by?
Detected by parathyroid, causing increased | PTH synthesis.
28
Increased PTH then causes?
Increased absorption of calcium by kidney Increased synthesis of Calcitriol Increased resorption of bone More calcitriol results in increased GI absorption of calcium
29
High Calcium detected by?
Detected by parafolicular cells of the thyroid, causing increased Calcitonin synthesis.
30
Increased Calcitonin then causes?
Decreased synthesis and secretion of PTH Decreased resorption of bone (opposing PTH) Shift to inactive form of Vitamin D Decreased PTH causes increased excretion of calcium
31
Hypoparathyroidism diseases?
Autoimmune disease rare, more common from thyroid surgery or parathyroid cancer. Very serious but treatable
32
Bioengineered hPTH now available for treatment of?
Hypoparathyroidism | short half-life (peptide).
33
Hypoparathyroidism most common treaatment?
More commonly treated with Vitamin D, with or without dietary supplements of calcium.
34
What is Teriparatide and what is its mechanism?
hrPTH 1-34 directly stimulates bone formation Excess endogenous PTH causes bone resorption Exogenous PTH in low doses increases bone formation without stimulating resorption.
35
Teriparatide can be used for?
Important for women with osteoporosis after bisphosphonate therapy
36
The function of Fibroblast Growth Factor 23 (FGF23) and it is produced by?
FGF23 inhibits production of 1, 25-(OH)2D3. Thus opposes PTH in kidney Produced by osteoclasts and osteoblasts
37
Calcitonin Mechanism of Action
Binds to plasma membrane receptor Decreases ruffled border surface area on osteoclasts Not a global inhibitor of PTH Has direct renal effects
38
Main Therapeutic uses of Calcitonin?
Hypercalcemia (as from Hyperparathyroidism) Paget’s disease (bone remodeling disorder) Now used in treatment of osteoporosis
39
Calcitonin very effective for?
* Short term treatment Hypercalcemia (as from Hyperparathyroidism). Prednisone can be used (takes 1 to 2 weeks) * Paget’s disease (bone remodeling disorder) * Now used as injection and nasal spray treatment for osteoporosis
40
With long-term use of Calcitonin?
Antibody development occurs (even with hCT)
41
Calcitriol is synthesised by and is the most important?
(1,25-Dihydroxy-D3) Synthesized by the skin & Transported in the blood. Most important calcium-regulating hormone and most important for therapeutics
42
Calcitriol Mechanism of Action
Stimulates Ca2+ and phosphate absorption in the small intestine Induces synthesis of calbindin (family of Ca2+ binding proteins) Binds to transcription factor to increase mRNA, protein synthesis Has additional effects to increase uptake of Ca2+ from intestine.
43
Major Uses of Calcitriol in Therapeutics
Prophylaxis and cure of nutritional rickets Treatment of metabolic rickets and osteomalacia Treatment of hypoparathyroidism Prevention and treatment of osteoporosis
44
What is Cholecalciferol and what is it found in?
= Vitamin D3 Found in fish liver oils. Takes effect in 12 to 24 hours. Remains in lipid stores for months.
45
Ergosterol is similar to?
cholesterol
46
Ergocalciferol is?
(after irradiation) = Vitamin D2
47
25-OH Cholecalciferol is
Vitamin D2
48
What is Calcipotriol & what is it more effective than?
Analog of Calcitriol used in treatment of Psoriasis topical. More effective than glucocorticoids.
49
What is Dihydrotachysterol & how effective is it?
Reduced Vitamin D2 , (DHT). It is 0.002 times as active as calcitriol, but more effective in high doses.
50
Dihydrotachysterol (DHT) now used in treatment of?
OSTEOPOROSIS either by Injection and nasal spray
51
Paricalcitol reduces?
PTH secretion
52
22-Oxacalcitriol supresses?
PTH gene expression.
53
Bisphosphonates are?
Nonhydrolyzable analogs of inorganic pyrophosphate
54
Bisphosphonates work by & are used to treat?
Inhibitors of bone resorption First used in Paget’s disease Effective in treatment of osteoporosis
55
Two Bisphosphonates that are not effective orally?
The drugs etidronate and pamidronate are not effective in management of hypercalcemia but a 4 to 24 hr infusion is effective in lowering calcium for several weeks.
56
Etidronate, alendronate, & risedronate used in?
Paget’s disease
57
Alendronate used for?
Osteoporosis
58
Etidronate, alendronate, & risedronate are absorbed and taken with?
All are absorbed very poorly in the intestine & must be taken after an overnight fast with a full glass of water. No food for 30 minutes. Now have weekly dosage form.
59
Alendronate Potency?
10-100X
60
Risedronate Potency?
1,000-10,000
61
Serious complication of bisphosphonates therapy?
Osteonecrosis of the Jaw 80% of cases follow dental extraction. Many cases are complicated by infection. Mainly in patients with cancer after prolonged therapy. Much more common with 3rd generation drugs.
62
Glucocorticoids are a common cause of?
Osteoporosis in adults by antagonize Ca uptake in intestine. Useful in reversing lymphoma-induced hypercalcemia
63
Estrogens are good for (blank), but increase the risk of (blank)?
Effective in preventing osteoporosis, but replacement therapy trials have shown increased risk of thrombosis.
64
Bisphosphonates have been demonstrated to prevent?
Cancer treatment induced bone loss.
65
Calcimimetics function?
Calcium Sensor Receptor Mimetics bind to the Calcium Sensor Receptor (CaSR)
66
Cinacalcet mechanism?
Binds allosterically to CaSR and allows PTH suppression at lower [Ca2+]. Effectively lowers circulating PTH.
67
Cinacalcet approved for?
Hyperparathyroidism in patients with parathyroid carcinoma.
68
Fluoride Potential agent in preventing?
Osteoporosis
69
Fluoride uses?
Long used for dental caries prevention | F – binds Calcium. Can be used to prevent blood clotting.
70
Fluoride Toxicity:
Osteosclerosis (hydroxyapatite replaced by fluoroapatite), mottled enamel (fluorosis).

Endocrine Pharmacology (5 decks)

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