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Bch 204 > Parathyroid hormone, calcitonin and cholecalciferol in Calcium homeostasis > Flashcards

Parathyroid hormone, calcitonin and cholecalciferol in Calcium homeostasis Flashcards

1
Q

Forms of Calcium
-The average young adult contains __g of calcium in their body, ___% of which is stored in bone, ____% in blood and ____% inside cells.

A

1200

99

  1. 99
  2. 01
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2
Q

Calcium in the blood exists in___ forms:

A

three

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3
Q

Forms of calcium in the blood

List them

____
____
_____

A

Free-ionised

  • Bound to anions
  • Bound to proteins
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4
Q

Forms of calcium in the blood

Free-ionised– (diffusible or not?) , (biologically active or not?)
*Bound to anionse.g. ____ – (diffusible or not?), (biologically active or not?)
*Bound to proteins(mainly ____) – ( diffusible or not?) ,( biologically active or not?)

A

Diffusible; active

phosphate; diffusible; not active

albumin;not diffusible; not active

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5
Q

Calcium Homeostasis

  • Calcium homeostasis is a complex process involving the following 4 key components:
  • serum ___, serum ____,______, and _____ hormone (PTH).
A

calcium

phosphate

1,25-dihydroxyvitamin D-3

parathyroid

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6
Q

More than 99% of the total body calcium is stored in ____ in the form of _____ and ______, predominantly as ______.

-Normally, a very (small or large?) portion of this calcium is available for exchange in the serum.

A

bone

phosphate; hydroxide salts

hydroxyapatite

Small

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7
Q 
Parathyroid hormone (PTH)
-Parathyroid hormone (PTH) is a \_\_\_peptide containing \_\_ amino acids that is secreted by the parathyroid glands after cleavage from \_\_\_parathyroid hormone (\_\_\_amino acids) to \_\_\_parathyroid hormone (\_\_\_amino acids) to the mature hormone.
A

poly; 84

prepro; 115

pro; 90

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8
Q

The major target end organs for parathyroid hormone (PTH) action are the ____, ____ system (___), and ____.

A

kidneys

skeletal; bones

intestine

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9
Q

Alternative names for parathyroid hormone;___;_____;____.

A

PTH

parathormone

parathyrin

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10
Q

Parathyroid hormone is secreted from four parathyroid glands, which are small glands in the neck, located ____ the thyroid gland.

A

behind

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11
Q

Feedback inhibition of parathyroid hormone (PTH) release occurs primarily by (direct or indirect ?) effect of ____ at the level of the____

A

Direct

calcium

parathyroid gland.

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12
Q

Major target organs of the PTH
Kidneys
-The primary response to parathyroid hormone (PTH) by the kidney is to______
-Parathyroid hormone also stimulates the production of _____in the kidneys.
-In the kidney, parathyroid hormone (PTH)____ reabsorption of phosphate in the____
-while ___ calcium reabsorption in the_____,____, and______.

A

increase renal calcium resorption

activevitamin D

blocks; proximal tubule

promoting; ascending loop of Henle; distal tubule; collecting tubule

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13
Q

PTH converts____ to its most active metabolite,______ , by activation of the enzyme _____in the _______ of the kidney.

A

25-hydroxyvitamin D

1,25-dihydroxyvitamin D-3

1-hydroxylase

proximal tubules

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14
Q

Major target organs of the PTH

Bones
-parathyroid hormone stimulates the ____ of calcium from large calcium stores in the bones into the _____.
-This increases bone ____ and (increases or decreases?) the formation of new bone.
-Parathyroid hormone (PTH) promotes absorption of calcium from the bone in 2 ways.
______ and ______

A

release

bloodstream

destruction

Decreases

Rapid phase and slow phase

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15
Q

The rapid phase of promotion of absorption of calcium from bone:
-brings about a rise in serum calcium within ____ and appears to occur at the level of the ____ and ______

A

minutes

osteoblasts and osteocytes.

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16
Q

Although it may seem counterintuitive that the cells that promote deposition of bone are involved in resorption,these cells form an interconnected network known as the_____ overlying the ____, but with a small layer of____ termed ____.
-When parathyroid hormone (PTH) binds to receptors on these cells, the ______ membrane pumps calcium ions from the ____ into the ______.

A

osteocytic membrane

bone matrix

interposed fluid

bone fluid

osteocytic ; bone fluid

extracellular fluid

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17
Q

The slow phase of promotion of absorption of calcium from bone:

  • occurs over ____ and has 2 components.
  • First, _____ are activated to ____ formed bone
  • Second, ____ of osteoclasts occurs.
A

several days

osteoclasts; digest

proliferation

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18
Q

mature and immature osteoclasts lack parathyroid hormone (PTH) membrane receptors
T/F

A

F

Only mature ones lack it

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19
Q

activation and proliferation of osteoclasts appear to be stimulated by _____ released by activated _____and _____ or by differentiation of (mature or immature?) osteoclast precursors that possess parathyroid hormone (PTH) and vitamin D receptors

A

cytokines

osteoblasts and osteocytes

Immature

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20
Q

Major target organs of the PTH

Intestine
-parathyroid hormone (directly or indirectly?) increases calcium absorption from food in the intestine, via its effects on ____ metabolism

A

Indirectly

vitamin D

21
Q

Facilitating calcium absorption from the small intestine would serve to _____ blood levels of calcium.

A

elevate

22
Q

Vitamin D induces synthesis of a_____ protein in____ cells that facilitates efficient absorption of calcium into blood.

A

calcium-binding

intestinal epithelial

23
Q

Although not well elucidated, 1,25-(OH)2D3 appears to exert a mild _____ effect on the parathyroid gland

A

inhibitory

24
Q

VITAMIN D

  • In concert with _____ hormone, vitamin D also enhances ____ of calcium out of bone.
  • it can either be made in the ____ from a ___-like precursor (______) by exposure to____ or can be provided ____ in the diet.
A

parathyroid

Absorption

skin; cholesterol

7-dehydrocholesterol; sunlight

pre-formed

25
Q

The version of vitamin D made in the skin is referred to as _____whereas the dietary form can be vitamin D3 (_____) or a closely related molecule of ___ origin known as vitamin D2(_____).

A

vitamin D3

cholecalciferol

plant; ergocalciferol

26
Q

The two forms of vitamin D(2 and 3) are metabolised (exact the same, differently or similarly?) in humans, are (equal or not?) in potency, and can be considered ____.

A

Similarly

Equal

equivalent

27
Q

It is now firmly established that vitamin D_is metabolised first in the __ to ____(25-OH-D or ____)
and subsequently in the _____ to _____to produce a biologically active hormone.

A

3

liver; 25-hydroxyvitamin-D ; calcidiol

kidneys; 1,25-(OH)2D (3)

28
Q

The 1,25-(OH)2D, like all vitamin D metabolites, is present in the blood complexed to vitamin D binding protein, a specific ____
-The 1,25-(OH)2D is believed to act on target cells similarly to the way a ____ hormone would act.

A

a-globulin.

steroid

29
Q

Free calcitriol hormone crosses the plasma membrane and interacts with a specific nuclear receptor known as the ____, a ___-binding, ____ protein with a molecular weight of _____.
-This ligand-receptor complex binds to a specific ____ and, with associated transcription factors (e.g.,_____), enhances transcription of mRNAs which code for _____ proteins,_____ proteins, or ____ proteins.

A

vitamin D receptor

DNA

zinc-finger

55,000

vitamin D-responsive element

retinoid X receptor

calcium-transporting ; bone matrix ; cell cycle-regulating

30
Q

1,25-(OH)2D stimulates intestinal absorption of ____ and ___ and mobilises them by stimulating bone ____.
-These functions serve the common purpose of restoring blood levels of ____ and ____to normal when concentrations of the two ions are low.

A

calcium and phosphate

resorption

calcium and phosphate

31
Q

-after normal calcium levels is reached , The further secretion of PTH is turned off not only by the ____, but also by a ____ feedback loop involving ____ (directly or indirectly?) suppressing PTH synthesis in the parathyroid gland.

A

feedback action of calcium

short; 1,25-(OH)2D

Directly

32
Q

Which is largely circulating and which is tightly regulated between

25-OH-D-1-aa-hydroxylase

And

25-OH-D.

A

25-OH-D-1-aa-hydroxylase is tightly regulated

25-OH-D is largely circulating

33
Q

CONTROL OF parathyroid hormone
-The parathyroid cell monitors extracellular free calcium concentration via an____ protein that functions as acalcium sensing receptor

A

integral membrane

34
Q

Primary Hyperparathyroidism

  • is the result of _____ disease
  • most commonly due to a ___(____) which secretes the hormone without proper regulation.
  • Common manifestations of this disorder are chronic elevations of blood calcium concentration (____),____ and_____ of bone
A

parathyroid gland

parathyroid tumor ; adenoma

hypercalcemia; kidney stones

decalcification

35
Q

Secondary Hyperparathyroidism

  • is the situation where disease _____leads to excessive secretion of parathyroid hormone.
  • A common cause of this disorder is ___ disease
  • if the kidneys are unable to reabsorb calcium, blood calcium levels will___, stimulating continual secretion of _____ hormone to maintain normal calcium levels in blood.
A

outside of the parathyroid gland

kidney

fall

parathyroid

36
Q

Secondary hyperparathyroidism result from inadequate nutrition

T/F

A

T

37
Q

diets that are deficient in calcium or vitamin D, or which contain excessive___ (e.g. all meat diets for ____).
-A prominent effect of secondary hyperparathyroidism is _____ of bone, leading to pathologic fractures or “ ____ bones”.

A

phosphorus

carnivore

decalcification

rubber

38
Q

Tertiary hyperparathyroidismis rare or common??

A

Rare

39
Q

Tertiary hyperparathyroidismcauses hypercalcaemia due to excess parathyroid hormone production as a result of ______

A

all four glands being overactive.

40
Q

Inadequate production of parathyroid hormone -hypoparathyroidism- typically results in decreased concentrations of ____ and increased concentrations of ____ in blood.

  • Common causes of this disorder include _____ and ____ that lead to destruction of parathyroid glands.
  • The resulting hypocalcemia often leads to ____and ____, and can be acutely life-threatening.
  • Treatment focuses on restoring normal blood calcium concentrations by calcium____,_____ and _____ therapy.
A

calcium

phosphorus

surgical removal of the parathyroid glands

diseases

tetany and convulsions

infusions; oral calcium supplements; vitamin D

41
Q

CALCITONIN

-is a hormone that functions to (elevate or reduce?) blood calcium levels.

A

reduce

42
Q

When the amount of calcium in blood rises above the normal range, ____cellsin the____gland secrete ____.

A

parafollicular

thyroid

calcitonin

43
Q

Calcitonin is secreted in response to hypercalcemia and has at least two effects:

  • (enhancement or Suppression?) of renal tubular reabsorption of calcium
  • (activation or Inhibition?) of bone resorption
A

Suppression

Inhibition

44
Q

calcitonin enhances excretion of calcium into urine.

T/F

A

T

45
Q

Calcitonin maximizes fluxes of calcium from bone into blood.

T/F

A

F

It minimizes it

46
Q

calcitonin has significant calcium-lowing effects in humans.

T/F

A

F

It has minimal influence on blood calcium levels in humans.

47
Q

During calcium deprivation Renal excretion of phosphate is _____ by ______

During calcium loading Renal excretion of phosphate is _____ due to______

A

Strongly stimulated by PTH

Decreased due to hypoparathyroidism

48
Q

Long-term deprivation of calcium leads to bone thinning

T/F

A

T

49
Q

High intestinal absorption and enhanced renal excretion , guards against hypercalcemia

T/F

A

F

Low intestinal absorption *

Bch 204 (14 decks)

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