Physiology of Calcium-Regulating Hormones (Toribio) Flashcards

1
Q

What is the most important calcium regulating hormone?

A

PTH

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2
Q

List the Functions of PTH:

A
  • Increases Blood calcium
  • Reduces blood Phosphorus
  • Activates vitamin D
  • Promotes bone remodeling
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3
Q

Mammals have ______ parathyroid glands
- Parathyroids III (caudal, internal, lower)
- Parathyroids IV (external, cranial, upper)

A

4

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4
Q

What are the 3 cell types of the Parathyroid glands?

A
  • Chief cells
  • Clear cells
  • Oxyphil cells
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5
Q

Fill in the blanks:

______________ produce PTH in response to hypocalcemia (Main cells)
_______________ are less active cells but secrete PTH
_______________ are inactive cells

(PTH = 84 aa, 1-34 is the active domain)

A
  • Chief cells
  • Clear cells
  • Oxyphil cells
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6
Q

(T/F) PTH receptor is present in renal tubular cells and osteoblasts

A

True

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7
Q

What controls PTH secretion?

A
  • Ca2+ concentrations
  • Calcium-sensing receptor
  • Vitamin D (1,25- dihydroxyvitamin D)
  • Phosphate (PO4, Pi) concentrations
  • Mg2+ concentrations
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8
Q

(T/F) Hypercalcemia increases PTH release

A

False, Hypocalcemia

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9
Q

(T/F) Stimulation by Ca2+ inhibits PTH secretion

A

True

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10
Q

(T/F) Vitamin D inhibits PTH synthesis and secretion, decreases parathyroid chief cell proliferation

A

True

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11
Q

(T/F) Hypophosphatemia stimulates PTH secretion

A

False, Hyperphospatemia

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12
Q

(T/F) Mag2+ facilitates Ca2+ homeostasis (PTH secretion and action)

A

True

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13
Q

PTH targets the:

A
  • Kidneys
    - Increases calcium reabsorption (and Mg reabsorption ThickAL)
    - Inhibits phosphate reabsorption (PCT) = increase excretion
    - Increases 1,25(OH)2D synthesis (tubular cells)
  • Bones
    - Increases bone resorption during hypocalcemia
    - PTH interacts with PTH receptors on osteoblasts to secrete factors that activate osteoclasts
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14
Q

PTH actions on bone resorption are indirect via ___________________

A

osteoblasts

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15
Q

Is a decoy receptor for RANKL to balance resorption and avoid excessive bone loss

A

OPG

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16
Q

________________ DO NOT have receptors for PTH but have receptors for calcitonin

A

Osteoclasts

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17
Q

The following is Hyperparathyroidism or Hypoparathyroidism?

Secondary
1. Sepsis (critically ill patients)
2. Hypomagnesemia

A

Hypoparathyroidism

18
Q

The following is Hyperparathyroidism or Hypoparathyroidism:

Secondary
1. Renal
2. Nutritional

A

Hyperparathyroidism

19
Q

Produced by the parafollicular cells (C Cells) of the thyroid gland in response to hypercalcemia

A

Calcitonin (CT)
- 32 aa
- decreases blood calcium
- decreases bone loss/resorption

20
Q

What controls calcitonin secretion?

A
  • Ca2+ concentrations
  • Stimulation by Ca2+ increases CT secretion
  • Gastrin
21
Q

(T/F) Hypocalcemia increases CT release

A

False, Hypercalcemia

22
Q

What is a strong stimulator of CT release?

23
Q

List the functions of vitamin D:

A
  • Increases calcium and phosphorus absorption and reabsorption
  • Modulates bone remodeling
  • Inhibits parathyroid cell function / PTH secretion
  • Regulates the immune function
24
Q

(T/F) Vitamin D is important for intestinal absorption and renal reabsorption of calcium

A

False, calcium AND phosphorus

25
(T/F) There is active vitamin D in milk
False, it would be a bad idea
26
(T/F) Vitamin D inhibits parathyroid chief cell proliferation, activity, and PTH secretion
True
27
Why do animals with chronic kidney disease have increased PTH concentrations?
The activation of vitamin D takes place in the Kidneys (the kidney suppresses PTH)
28
(T/F) PTHrP is not important for development of animals
False
29
Low calcium stimulates ________________ secretion
PTH
30
Vitamin D is activated in the ____________ by ___________________
kidney, 1alpha-hydroxylase
31
Osteoclast activation requires PTH binding to _________________
osteoblast
32
Vitamin D stimulates renal reabsorption of ________________
Calcium and phosphorus
33
Vitamin D stimulates intestinal absorption of ________________
Calcium and Phosphate
34
PTH increases paracellular calcium reabsorption by _________________
binding to its receptor in the renal tubular cell, specifically in the TAL, by making the lumen more positive
35
If serum PTH concentrations are elevated, what is expected?
Increased renal excretion of phosphorus and increased reabsorption of calcium
36
What are some important things about magnesium?
- It is important for the synthesis and action of PTH - PTH increases its renal reabsorption - Contributes to energy homeostasis
37
(T/F) Unlike calcium, magnesium is minimally stored in bone
False
38
(T/F) In the lactating animal, parathyroid hormone-related protein (PTHrP) is produced by the mammary gland to reduce/stop bone resorption
False
39
What makes renal tubules electropositive?
PTH
40
What binds receptors on osteoclasts?
Calcitonin
41
What promotes the absorption of phosphorus?
Vitamin D
42
Where is PTHrP secreted?
It is secreted by multiple tissues