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PHYL2064 > Endocrine L3: PTH > Flashcards

Endocrine L3: PTH Flashcards

1
Q

What are 8 functions of calcium that are important for physiological processes?

A
  1. Structural component of bones and teeth
  2. Contributes to restin g p membrane potential
  3. Maintains normal excitability of nerve & muscle cells
  4. Involved in neurotransmitter & hormone release
  5. Muscle contraction (skeletal)
  6. Activation of many enzymes
  7. Coagulation of blood
  8. Milk production
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2
Q

What is the distribution of calcium in the body?

A
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3
Q

99% of calcium is found in the _____ and ____, This means that they are fairly stable.

A

bones; teeth

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4
Q

What are 3 regulators of calcium?

A

Depends on hormonal control – balance maintained between ECF and three body maintained between ECF and three body compartments

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5
Q

What are the 2 types of control for the regulation of calcium?

A
  1. Acute control
  2. Chronic control
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6
Q

What are 2 characteristics of acute control in the regulation of calcium?

A
  1. Must maintain constant free Ca++ concentration in plasma concentration in plasma
  2. Mostly by rapid exchange between bone and ECF and ECF

Used all the time

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7
Q

What are 2 characteristics of acute control in the regulation of calcium?

A
  1. Maintain total Ca++ level in body long-term Adjust gastrointestinal absorption and urinary excretion
  2. Only when need to change total Ca++ level
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8
Q

When is acute control in the regulation of calcium use vs chronic control?

A

Acute: All the time

Chronic: Only when need to change total Ca++ level

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9
Q

What are the 3 hormones that regulate Ca++ metabolism?

A
  1. Parathyroid Hormone (PTH)
  2. Vitamin D3
  3. Calcitonin

Other involved include steroids, thyroid hormones, GH and other local fac tors

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10
Q

Is parathyroid hormone related to thryoid hormone?

A

Not thyroid hormone (not related at all) = Comes from the parathyroid gland which happens to be next to the thyroid glands

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11
Q

What hormone is the most important for releasing Ca++?

A

Parathyroid hormone (PTH)

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12
Q

What are 3 types of cells that are important for bone formation and resorption?

A
  1. Osteoblasts
  2. Osteoclasts
  3. Osteocytes
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13
Q

What are osteoblasts?

A

synthesise and secrete collagen synthesise and secrete collagen & promote deposition of CaPO4 crystals

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14
Q

What are osteoclasts?

A

promote resorption of bone

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15
Q

What are osteocytes?

A

essential role in exchange of Calcium between ECF & bone

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16
Q

What does the structure of bone look like?

A
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17
Q

What does fast and slow exchange of Ca+ from mineralised bone to plasma look like?

A
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18
Q

What are 6 characteristics of the parathyroid hormone?

A
  1. Parathyroid glands are 4 small glands located on the posterior glands located on the posterior surface of the thyroid gland
  2. PTH secreted from chief cells in direct response to changing plasma Ca++ concentrations
  3. Overall Ca Overall Ca++ PO in plasma
  4. PTH is a peptide, 84 amino acid chain
  5. Half -life in plasma of <20 minutes life in plasma of <20 minutes
  6. Actions on bone, kidneys & GIT
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19
Q

Parathyroid glands are ____ small glands located on the______ glands located on the posterior surface of the thyroid gland

A

4; posterior

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20
Q

PTH secreted from _____ cells in direct response to changing plasma _____ concentrations

A

chief; Ca++

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21
Q

Overall, there is a _____ (increase/decrease) Ca++ and ____ (increase/decrease) PO in plasma

A

increase; decrease

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22
Q

PTH is a ____ with 84_____ chain

A

peptide; amino acids

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23
Q

PTH has a half-life in plasma of <20 minutes. What does that mean?

A

Very short/fast acting

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24
Q

What is the short term function of parathyroid hormone on bone?

A

Stimulates Ca++ membrane pump in membrane pump in osteocytes, so Ca++ moves from bone fluid to plasma in central canal

  • Stimulates Ca++ transporters
25
Q

What is the long term function of parathyroid hormone on bone?

A

stimulates osteoclasts (Bone starts to get broken down) inhibits stimulates osteoclasts, inhibits osteoblasts, so Ca++ and PO 4 increase in plasma (Bone starts to get broken down)

26
Q

What is function of parathyroid hormone on the kidneys?

A

Retain more Ca++ from reabsoption

Decreases Ca++ loss - increased tubular reabsorption of Ca++ and decreased tubular reabsorption of PO4

  • Getting phosphate from bone and this level needs to be decreased
27
Q

What is function of parathyroid hormone on the GIT?

A

Indirectly increases Ca++ and PO4 – increases absorption by small intestine by stimulating activation of Vitamin D 3

Vitamin D3 can be eaten in diet or can be produced naturally by the body

28
Q

Most ingested Ca++ ____ (is/is not) absorbed by GIT, but lost in faeces lost in faece

A

is not

29
Q

How can Vit D be available?

A

Can eat it or produce it naturally… that is why we need sunlight on skin (make Vit.D in response to sunlight

30
Q

Why do we need sunlight on our skin?

A

make Vit.D in response to sunlight

31
Q

Vitamin D is produced either in the ___ or ____, and is activated by the ____ and ___ to 1,25 dihyroxycholecalciferol (Vitamin D3)

A

skin; ingested; liver; kidney

32
Q

What are 4 functions of Vitamin D?

A
  1. promotes absorption of Ca ++
  2. promotes absorption of Ca++ from the intestine by from the intestine by increasing its transport across intestinal epithelium
  3. promotes absorption of PO4 in intestine increases bone resorption
  4. stimulates Ca++ & PO4 reabsorption in kidneys
33
Q

What happens when you don’t get enough sunlight?

A

Decreased vitamin D and that means decreased Ca++

34
Q

How does Vit. D help Ca++ and PO43-?

A
35
Q

____ has the opposite role to vit. D and PTH

A

Calcitonin

36
Q

Calcitonin is produced in the ____ cells of the ____gland in response to high plasma Ca++ levels

A

C; thyroid

37
Q

What is something special about calcitonin?

A

Doesn’t usually exists and is only produced when body needs it Increased Ca++ levels are quite rare

38
Q

What are the 2 functions of calcitonin?

A
  1. decreases bone resorption (effects osteoclasts)
  2. decreases Ca++ reabsorption in kidneys, promotes increased excretion
39
Q

What is the overall action of action?

A

Increase Ca++ and decrease PO in plasma

40
Q

Calcitonin protects against _____.

A

hypercalcemia If Ca++ levels become ahigh (while its quite rare)

41
Q

How can calcitonin be used clinically?

A

Can give a synthetic amount to decrease Ca++ levels

42
Q

What are 3 mechanism to help improve Ca++ levels?

A
43
Q

What are the 2 main abnormalities of calcium metabolism?

A
  1. PTH hypersecretion (hyperparathyroidism)
  2. PTH hyposecretion (hypoparathyroidism)
44
Q

What are 6 features of PTH hypersecretion (hyperparathyroidism)?

A
  1. Most frequently caused by PTH Most frequently caused by PTH -secreting adenomas leads to hypercalcemia
  2. Increased Ca++ mobilisation from bones causes mobilisation from bones causes softening & fractures
  3. Increased Ca++ excretion through kidneys cause polyuria (Urinate a lot), polydipsia (Very thirsty = drink a lot) and nephrocalcinosis (Formation of kidney stones made of Ca++)
  4. Decreased excitability of nerves & muscles leads to weakness, depression & coma
  5. Hypercalcemia leads to nausea, constipation &increased
  6. incidence of peptic ulcers
45
Q

What is PTH hypersecretion abnormality (hyperparathyroidism) usually called? Why?

A

“Bones, stones and groans”

  • Weakening of bones, kidney stones and upset tummy (GIT)
46
Q

What do the bones for a person with hypothyroidism look like?

A

Developing holes in their bones = completely lost CaPO4 crystals

47
Q

What are 5 features of PTH hyposecretion (hypoparathyroidism)?

A
  1. Most frequently caused by gland destruction, leads to severe hypocalcemia
  2. Parathyroid glands are essential for life
  3. Hypocalcemia causes increased nerve & muscle excit bilit it ability
  4. Severe hypocalcemia leads to death by asphyxiation caused by laryngospasm caused by laryngospasm
  5. Mild hypocalcemia causes cramps, twitches & tingles ( tingles ( pins ‘ and needles and needles’ sensation)
48
Q

What is PTH hyposecretion (hypoparathyroidism) frequently caused by?

A

gland destruction, leads to severe hypocalcemia

49
Q

What is PTH hypersecretion (hyperparathyroidism) frequently caused by?

A

by PTH -secreting adenomas secreting adenomas, leads to hypercalcemia

50
Q

What are 4 other causes for hypocalcemia apart from PTH hyposecretion?

A
  1. High demand for Ca++ in pregnancy/lactation – causes tetany or paralysis
  2. Lack of Vitamin D/sunlight- causes rickets in children, osteomalacia in adults
  3. Change in blood pH- alkalosis (less free Ca++)
  4. Pancreatitis
51
Q

Condition of low bone mass & structural disruption that results in fractures after minimal trauma that results in fractures after minimal trauma are especially prevalent in______ ______ (men/women) but can occur in all aged population

A

post-menopausal women;

52
Q

What are 4 common fracture sites in osteoporosis?

A
  1. vertebral bodies
  2. distal radius
  3. neck of femur
  4. ribs
53
Q

Why do post menopausal women have a decline in bone mass and density?

A

Loss of estrogen = protective of bone mass

  • Loss bone mass
  • Increased risk of fracture
54
Q

Drinking ____ (eg. ____) can inhibit Ca++ uptake and laying down of bone mass. What does that impact?

A

PO43- (coke/coca cola) = never reach peak

55
Q

What is 4 features that influence bone mass gain?

A
  1. genetic factors
  2. physical activity
  3. Ca++ intake
  4. hormones – esp oestradiol
56
Q

What are 5 risk factors which reduce the maintenance of bone mass in ageing?

A
  1. toxic exposure
  2. smoking
  3. alcohol excess
  4. immobility
  5. glucocorticoids
57
Q

In ageing, bone ____ declines prior to accompanying measurable loss in density

A

strength

58
Q

What are 5 treatments for the prevention of osteoporosis?

A
  1. Regular exercise (especially weight bearing)
  2. Nutrition in growing phase (Ca++ & Vitamin D)
  3. Post-menopause – HRT (but side-effects & increased risk CV disease and cancer)
  4. Androgens & SERMs (selective-oestrogen receptor modulators)
  5. Calcitonin

PHYL2064 (29 decks)

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