Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

IC 1.0 > Calcium Homeostasis > Flashcards

Calcium Homeostasis Flashcards

1
Q

How does PTH affect calcium homeostasis?

A
  • initiates conversion activation of D3 in the kidneys
  • promotes phosphorous excretion and calcium reabsorption in the kidney
  • promotes bone recycling (osteoclast and osteoblast activity)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the effect of activated vitamin D on calcium homeostasis?

A
  • promotes bone recycling (osteoclast and osteoblast activity)
  • promotes absorption of calcium and phosphorous from the gut
  • promotes reabsorption of calcium and phosphorus from the renal tubules
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Through what mechanism do PTH and activated VitD affect bone mineral homeostasis?

A
  • promote differentiation of preosteoclasts
  • promote differentiation of preosteoblasts
  • promote activation of osteoblasts, which release RANK-L and activate osteoclasts as well
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are four important biologic actions of calcium?

A
  • clotting of blood
  • ossification of bone
  • muscle contraction
  • release of endocrine hormones and neurotransmitters
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How does hypercalcemia present?

A

generalized weakness and smooth muscle dysfunction

  • stones, bones, groans, thrones, and psych overtones
  • renal stones, bone pain, abdominal pain, urinary frequency, anxiety and altered mental status
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does hypocalcemia present?

A
  • tetany
  • QT prolongation
  • seizures
  • Chvostek and Trousseau sign
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the two primary pharmacological uses of calcium supplements?

A
  • treat hypocalcemia due to dietary insufficiency, malabsorption, renal disease, or hypoparathyroidism
  • prophylaxis and treatment of osteoporosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the dietary recommendations for calcium intake?

A
  • 1000 mg/day for most adults

- 1200 mg/day for women over 50 and men over 70

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Calcium Carbonate

A
  • an oral calcium supplement
  • commonly used because it is cheap and the pills are small
  • but is more likely to cause gas, bloating, and constipation
  • also neutralizes gastric acid and can cause rebound acid secretion
  • need to take with food
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does calcium citrate compare to calcium carbonate?

A
  • both are oral preparations of calcium
  • carbonate is cheaper and more concentrated so pills are smaller
  • citrate has fewer GI problems, does not affect gastric pH, and can be taken without food
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the downsides of calcium gluconate?

A
  • it can be irritating to the veins (but is least likely of the IV preparations)
  • rapid infusion can cause arrhythmias
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Rapid infusion of calcium can cause what adverse effect?

A

arrhythmias

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

By what mechanism do bisphosphonates impact calcium homeostasis?

A
  • they are pyrophosphate analogs in which the P-O-P bond has been replaced with a non-hydrolyzable P-C-P bond
  • they suppress the activity of osteoclasts by inhibiting formation and dissolution of hydroxyapatite crystals
  • they also inhibit farsenyl pyrophosphate synthase, which also impairs osteoclast activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

BIsphosphonates

A
  • pyrophosphate analogs used to promote bone formation and inhibit resorption
  • they suppress the activity of osteoclasts by impairing formation and dissolution of hydroxyapatite crystals and by inhibiting farsenyl pyrophosphate synthase
  • used for osteoporosis, bone metastases, Paget’s disease of bone, and hypercalcemia
  • poor oral absorption, so taken with a full glass of water without food, and remain standing for 30 minutes
  • may cause esophageal and gastric irritation, adynamic bone (“bad bone”), osteonecrosis of the jaw, or renal failure
  • adynamic bone and osteonecrosis are why continuous use for more than five years is not recommended; should take a “drug holiday”
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the primary uses of bisphosphonates?

A
  • osteoporosis
  • bone metastases
  • Paget’s disease
  • hypercalcemia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do etidronate, alendronate, and risedronate compare?

A
  • all are oral bisphosphonates
  • etidronate < alendronate < risedronate half life
  • etidronate is limited to those with Paget’s disease
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is unique about etidronate?

A

it is a bisphosphonate with a relatively short half life (1x daily dosing) that is only used for those with Paget’s disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is unique about pamidronate?

A

it is a bisphosphonate used only in those with Paget’s disease or a malignancy

19
Q

How do glucocorticoids affect calcium homeostasis?

A
  • they decrease calcium absorption and increase excretion

- may lead to osteoporosis

20
Q

How do thiazide diuretics impact calcium homeostasis?

A
  • decrease renal calcium excretion, augmenting the effects of PTH
  • used for those with hypercalciura and calcium-based nephrolithiasis
21
Q

What use does raloxifene have in calcium homeostasis? What class of drug is it?

A

a SERM used for the treatment of osteoporosis

22
Q

Teriparatide

A
  • a recombinant form of PTH
  • stimulates new bone that is structurally normal
  • not recommended for more than 2 years because of a black box warning for osteosarcoma
  • administered subcutaneously
23
Q

How does calcitonin affect calcium homeostasis?

A

it tends to counteract PTH

  • it impairs bone resorption without impacting deposition
  • it promotes renal excretion of calcium and phosphate
24
Q

How is calcitonin used pharmacologically?

A
  • it is used to increase bone mass because it inhibits resorption much like bisphosphonate
  • it is not as effective as bisphosphonates or teriparatide
25
Q

Denosumab?

A
  • a monoclonal antibody that inhibits RANKL
  • suppresses bone resorption
  • may have immunosuppressive side effects
  • administered subcutaneously on a biannual basis
26
Q

How are androgens and estrogens used for treatment of calcium homeostasis?

A
  • they reduce the bone-resorbing effects of PTH
  • used in the treatment of osteoporosis
  • but not recommended for postmenopausal women because of their effects on breast, uterus, and CV system
  • testosterone is first converted to estrogen
27
Q

How does fluoride improve calcium homeostasis?

A
  • it stabilizes hydroxyapatite crystals in bone and teeth
  • used to prevent dental caries
  • experimental use for osteoporosis
  • toxicity occurs well beyond the level found in drinking water but presents with GI pain, n/v, and headaches
28
Q

Cinacalcet

A
  • a drug affecting calcium homeostasis
  • activates the calcium-sensing receptor on the parathyroid gland and suppresses PTH release
  • used for secondary hyperparathyroidism: renal disease and parathyroid carcinoma
29
Q

Where do we get vitamin D naturally?

A
  • D3 is formed in the skin by UV irradiation

- D2 and D3 can also be found in the diet

30
Q

What is the most active form of vitamin D?

A

1,25(OH2)D3, also known as calcitriol

31
Q

What is calcitriol?

A

1,25(OH2)D3, the most active form of vitamin D

32
Q

What is the recommended serum level for Vitamin D?

A

30-70 ng/mL

33
Q

Vitamin D deficiency in children causes what disease?

A

Rickets with abnormal and retarded bone growth

34
Q

How does Vitamin D toxicity manifest?

A

very difficult to achieve but presents with hypercalcemia, hypercalciuria, n/v, decreased appetite, frequent urination, and renal failure

35
Q

What are the following also known as:

  • cholecalciferol
  • ergocalciferol
  • calcitriol
  • calcipotriene
  • doxercalciferol
  • paracalcitrol
A
  • cholecalciferol: D3
  • ergocalciferol: D2
  • calcitriol: 1,25(OH)2D3
  • calcipotriene: no aka
  • doxercalciferol: 1a-(OH)D2
  • paracalcitrol: 19-nor-1,25(OH)D2
36
Q

Under what circumstances wouldn’t you use D3 to supplement a vitamin D3 deficient patient?

A

if they can’t convert it to calcitriol on their own

37
Q

What are the most common causes of vitamin D deficiency?

A
  • inadequate intake
  • inadequate exposure to sunlight
  • renal dysfunction
  • administration of anticonvulsants that increase metabolic of 25(OH)D
38
Q

What are the clinical uses of Vitamin D?

A
  • treatment and prophylaxis of nutritional rickets
  • treatment of metabolic rickets secondary to renal hydroxylase deficiency or chronic renal failure (prevents calcitriol formation)
  • osteoporosis and osteomalacia in combination with calcium supplementation
  • psoriasis
  • hypoparathyroidism
  • secondary hyperparathyroidism in renal disease
39
Q

What form of vitamin D supplement is used to treat psoriasis?

A

topical calcipotriene

40
Q

What is metabolic rickets?

A

a genetic defect in renal hydroxylase or chronic renal failure, which prevent endogenous production of calcitriol from D2/D3

41
Q

How is vitamin D supplementation used in the treatment secondary hyperparathyroidism in renal disease?

A
  • these patients have low 1,25(OH)2D

- treat with doxercalciferol or paracalcitrol

42
Q

What are doxercalciferol and paracalcitrol used to treat?

A

secondary hyperparathyroidism due to renal disease

43
Q

What are the advantages/disadvantages of supplementing with D2 versus D3?

A
  • D3 is more effective at increasing plasma D concentrations
  • has a longer half life and higher affinity for receptors in human tissue
  • however, it is over the counter
  • as a result, D2, which is a prescription, is used more frequently because the formulation is more regulated and reliable despite being less effective
  • additionally D3 is derived from animal sources and may be objectionable to vegans

IC 1.0 (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions