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1.2.4. Metabolism, Endocrinology, Haematology > Calcium Metabolism > Flashcards

Calcium Metabolism Flashcards

1
Q

Explain the significance of maintaining serum calcium levels within set limits

A
  • Maintains bones teeth
  • Reg HR
  • Eases insomnia
  • Regulates passage of nutrients in/out of the cells walls
  • Lowers BP
  • Reduces blood cholesterol levels
  • Intracellular signalling pathways
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2
Q

Describe the hormonal regulation of serum calcium by PTH

A

PTH = active when serum [Ca2+] low

1) Stim osteoclast activity = release of Pi and Ca
2) Stim Ca reabsorption in kidney and excretion of phosphate (stops crystal formation)
3) Stim conversion of Vit D to active form = increase Ca absorption

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3
Q

Describe the hormonal regulation of serum calcium by calcitriol (active vit D)

A

High Ca = lowered calcitriol = less Ca2+ taken from gut

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4
Q

Describe the hormonal regulation of serum calcium by Vit D

A

Increased intestinal Ca absorption

Increases renal Ca reabsorption

Increases bone resorption

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5
Q

What reaction occurs to activate Vit D?

A

2 hydroxilation reactions

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6
Q

What is the role of calcitonin?

A

Counteracts effects of PTH

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7
Q

What is the feedback regulation for increased plasma [Ca]?

A

PTH lowers

Bone = increased bone building, decreased bone breakdown

Kidney = lowers calcitriol levels, lowers kidney Ca reabsorption

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8
Q

What cells prod PTH?

A

Chief cells in the parathyroid gland

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9
Q

Explain the regulation of parathyroid hormone

A

Low serum Ca up-reg gene transcription + prolongs survival of mRNA

High serum calcium down-reg gene transcription

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10
Q

Outline the secretion of PTH

A

GPCR

High [Ca] binds

Slows/inhibs release of PTH

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11
Q

What is the role of hydroxyapatite crystals?

A

Mineralises collagen matrix produced by osteoblasts

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12
Q

Explain the regulation of vit D

A

PTH stim amount of conversion of vit D to active form

Therefore increases the absorption of Ca2+

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13
Q

Explain the significance of renal function on calcium metabolism

A

Ascending limb/DCT = Ca reabsorption

Thick ascending limb = P inhibited reabsorption

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14
Q

What factor is Ca in the clotting cascade?

A

IV

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15
Q

What Ca chelator needs to be added to blood samples to inhibit clotting?

A

EDTA

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16
Q

What is added to donor blood packs to stop clotting, and what does this then mean?

A

Citrate chelates Ca ions

Massive blood transfusions therefore require IV Ca

17
Q

What is the most common cause of hypercalcemia in a hospital setting?

A

Malignant osteolytic bone mets

Multiple myeloma

18
Q

What cancers met to bone causing lytic lesions?

A

Breast, lung, renal, thyroid

= lytic and therefore cause hypercalcemia

19
Q

What is the most common cause of osteoblastic bone met?

A

Prostate cancer

= osteoblastic therefore NO hypercalcemia

20
Q

What are the common sites for bone mets?

A

Vertebrae, pelvis, proximal femur, ribs, proximal humerus, skull

21
Q

Outline primary hyperparathyroidism

A

1 of the 4 glands devel adenoma

= prod excessive PTH = serum Ca rise and serum Phos to fall

22
Q

Outline secondary hyperparathyroidism

A

All four glands hyperplastic = think no enough Ca

Vit D def = low Ca = high PTH = activates osteoclasts = mobilise Ca from bone = bone pain, osteomalacia

Vit D def due to chronic renal failure = renal osteodystrophy

23
Q

What is serum alkaline phospatase?

A

Marker of high bone turnover

24
Q

What are the symptoms of primary hyperparathyroidism?

A

Moans, groans, stones, bones

25
Q

What are the symptoms of severe hypercalcemia?

A

High Ca in polyuria = dehydration = rehydration the main treatment

26
Q

When is hypocalcemia most commonly seen?

A

Post total-thyroidectomy

27
Q

What is the most dangerous concern regarding hypocalcemia?

A

Can kill due to laryngeal muscle tetany (spasm)

28
Q

How does Ca change neuronal activity?

A

Hyper = suppression of neuronal activity: lethargy, confusion, coma

Hypo = excitable nerve: tingling, muscle tetany, epilepsy

29
Q

What is osteoporosis?

A

Decreased bone density with normal ratio of mineral to matrix
= normal bone but not enough of it

30
Q

What is osteomalacia?

A

Ratio of mineral to matrix is decreased

= soft bones that are prone to bending

31
Q

What are the risk factors for osteoporosis?

A

Postmenopausal women, low BMI, long-term oral steroid use, heavy drinking, smoking, low BMI, prolonged inactivity

1.2.4. Metabolism, Endocrinology, Haematology (21 decks)

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