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Biochemistry > Calcium Regulation > Flashcards

Calcium Regulation Flashcards

1
Q

________ are very sensitive to changes in calcium ion concentration.

A

Neurons

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2
Q

Hypercalcaemia causes progressive ________ of the nervous system.

A

Depression

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3
Q

Calcium is released from _______________when ______concentration decreases

A

Bones
ECF

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4
Q

50% of calcium is bound to ____________.

A

Albumin

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5
Q

Physiological functions expend on ____________, NOT total.

A

Ionised

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6
Q

What is the preferred specimen for total Ca2+?

A

Serum or lithium heparin-plasma

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7
Q

Two methods for Ca2+ detection

A

AAS - CPC and Ca2+ forms complex, Ca2+ is released from protein carrier by acidification of the sample before dye-binding reaction, uses 8-hydroxyquinoline to prevent Mg2+ interference (rarely used clinically)

ISE - membranes that selectively and reversible bind Ca2+, as Ca2+ binds electric potential develops that is proportional to ionised Ca2+ concentration

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8
Q

Adjusting for albumin

A

Serum concentrations of albumin must be considered when assessing serum calcium levels
Labs use a calculation

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9
Q

Negative CA2+ balance

A

Output > intake => osteoporosis

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10
Q

Positive CA2+ balance

A

Intake > output => occurs during growth

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11
Q

What are the three organ systems important in CA2+ metabolism?

A

Skeleton
GI tract
Kidney

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12
Q

4x Calcitropic hormones

A

PTH
Vitamin D
Calcitonin
PTHrP

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13
Q

PTH

A

Made in parathyroid
Tight feedback between PTH release and serum CA2+

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14
Q

How many parathyroid glands do you have?

A

4

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15
Q

What regulates PTH secretion?

A

Extracellular CA2+

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16
Q

Low CA2+ _____________PTH

A

Increases

17
Q

CA2+ regulates transcription of PTH via _________.

A

CaSR

18
Q

High levels of ________ inhibit transcription of PTH.

A

Vitamin D3

19
Q

4 actions of PTH

A

Bone
Stimulates Ca2+-release via initial osteocyte mobilisation of Ca2+ from bone to ECF
Then continued, slow release of bone Ca2+ and phosphate from osteoclastic breakdown of bone matrix

Kidney
1. increases CA2+ reabsorption in renal tubules
2. stimulates urinary phosphate excretion
3. stimulates transcription of 1-alpha hydroxylase for vitamin D activation to active form calcitrol

20
Q

Vitamin D

A

Vit D2 => food
Vit D3 => skin via UVB rays
Promotes CA2+ absorption in GI tract and deposition in bone
Absorption greater at lower pH

21
Q

How is vitamin D activated?

A

25-hydroxylase in liver converts D3 -> D
1alpha-hydroxylase (requiring PTH) in kidney converts D -> active metabolite

22
Q

Patients with CKD fail to activate ________leading to bone disease,

A

Vitamin D

23
Q

Two stimulus for vitamin D formation

A
  1. PTH
  2. Low plasma phosphate
24
Q

Rickets

A

Vit D deficiency
Osteomalacia
Osteoporosis

25
Q

Vitamin D-resistant rickets

A

Deficiency of 1alpha-hydroxylase
Sex linked on X-chromosome
Renal tubular defect of phosphate resorption
Teeth may be hypoplastic and eruption affected

26
Q

Calcitonin

A

1. Source
Released from parafollicular C cells in the thyroid
2. Bone
Reduces rate of release of CA2+ to ECF
3. Secretion
Secreted during hypercalcemia, may protect against abnormal rises
4. Normal physiology
Minimal in normal control, if any, role in normal control of CA2+

27
Q

High calcium/vit D intake

A

PTH and active vit D are downregulated
Serum calcium remains normal -> good quality bones formed

28
Q

Low calcium/vit D intake

A

PTH is upregulated
Poor quality bones -> liable to fracture

29
Q

Hypocalcemia causes x3

A

Parathyroid glands don’t work
Parathyroid glands work, but PTH receptor signalling doesn’t
Renal failure

30
Q

Management of hypocalcaemia

A

Oral/IV calcium and correct underlying cause

31
Q

________ required for normal function of both parathyroid glands and PTH.

A

Mg2+

32
Q

Causes of Hypercalcemia

A

Multiple myeloma
Hyperthyroidism
Benign familial hypocalciuric hypercalcemia

PTH is fully suppressed, if still detectable then hyperparathyroidism

33
Q

___________ promote urinary calcium excretion and stabilise bone

A

Bisphoshphate

34
Q

Parathyroid hormone related protein

A

PTHrP
Blood calcium is increased
Not sensitive to feedback regulation by CA2+

35
Q

Call ward when calcium levels

A

<1.8mmol/L
>3.5mmol/L

Biochemistry (19 decks)

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