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Parathyroid, regulation of calcium Flashcards

1
Q

Good indicators of calcium availability

A

Albumin levels (Ca binds to calcium)

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2
Q

Net uptake of calcium in humans

A

200 mg/day

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3
Q

Number of parathyroid glands in humans

A

4

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4
Q

Typical calcium levels

A

2.6 - 2.6 mM
8.8 - 10.3 gm/100mL
(tightly regulated)

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5
Q

Chief cells (parathyroid gland) synthesize _________

A

PTH

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6
Q

Chief cells (gastric) release __________

A

Pepsinogen, gastric lipase

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7
Q

Chief cells (gastric) release __________

A

Pepsinogen, gastric lipase

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8
Q

Biologically active fragment in PTH

A

N-terminal fragment 1-34. Binds to PTH receptor

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9
Q

Cells present in parathyroid

A

Chief cells, oxyphil cells (no known function)

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10
Q

Biologically inactive fragment in PTH

A

C-terminal fragment 35-84 (cleaved quickly)

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11
Q

PTHrP function

A

Mimics action of PTH in bone and kidney

NOT a regulator of plasma Ca2+

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12
Q

Do tumors produce PTHrP?

A

Yes, resulting in hypercalcemia

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13
Q

PTH receptors

A

PTH 1R = primary receptor. Located in osteoblasts and kidney. G-coupled. Binds N-terminal 1-34 and PTHrP
PTH 2R = secondary. Binds N-terminal 1-34, but does NOT bind PTHrP

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14
Q

Effect of PTH

A

Increase serum Ca2+, decrease plasma Pi

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15
Q

These express PTH receptors

A

Osteoblasts

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16
Q

Do not express PTH receptors

A

Osteoclasts

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17
Q

Bone formation and mineralization

A

Osteoblasts

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18
Q

Bone reabsorption

A

Osteoclasts

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19
Q

Osteocytes

A

Relatively inert; may exert control over osteoblasts/osteoclasts. Also able to destroy bone through rapid process

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20
Q

PTH stimulates _________ in osteoblasts

A

M-CSF (macrophage - colony stimulating factor)

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21
Q

Mediates the differentiation of osteoclast precursors

A

M-CSF

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22
Q

_____ stimulates RANK ligand

23
Q

Function of RANK ligand

A

Osteoclast differentiation

24
Q

Antagonist of RANKL

A

Osteoprotegerin (OPG)

25
Q

Stimulator of OPG

A

Estrogen (promotes bone health, prevents osteoporosis)

26
Q

Inhibitor of OPG

A

Cortisol, other glucosteroids

27
Q

Inhibitor of OPG

A

Cortisol, other glucosteroids

28
Q

RANKL stands for

A

Receptor activator of nuclear factor kappa-B ligand

29
Q

PTH action in the kidney

A 
Stimulates CYP1alpha (converts active form of Vitamin D3)
Stimulates Ca2+ channel insertion in apical membrane of distal tubule
30
Q

PTH action in the kidney

A

1) Stimulates CYP1alpha, which encodes 1alpha-hydroxylase (converts active form of Vitamin D3)
2) Stimulates Ca2+ channel insertion in apical membrane of distal tubule
3) Reduces phosphate reabsorption in both tubules, but especially in the proximal tubule

31
Q

Site of action of PTH in kidney

A

Distal nephron, TAL of Loop of Henle. Distal and proximal tubules of the kidney

32
Q

Site of action of PTH in kidney

A

Distal nephron, TAL of Loop of Henle. Distal and proximal tubules of the kidney

33
Q

PTH regulation sites

A

Chief cells, kidney tubules, and C cells

34
Q

C cell function

A

Secretion of calcitonin

35
Q

CaSR role

A

Inhibits PTH synthesis at promoter level, and stimulates degradation of preformed PTH

36
Q

Vitamin D

A

Binds nuclear receptor - VDR
Inhibits PTH synthesis at promoter level (direct)
Stimulates CaSR gene transcription (indirect regulation of PTH)

37
Q

CaSR role

A 
Binds ionized (free) Ca2+
Inhibits PTH synthesis at promoter level, and stimulates degradation of preformed PTH
38
Q

Vitamin D function

A

Binds nuclear receptor - VDR
Inhibits PTH synthesis at promoter level (direct)
Stimulates CaSR gene transcription (indirect regulation of PTH)

39
Q

Vitamin D function (calcitriol)

A

Binds nuclear receptor - VDR
Inhibits PTH synthesis at promoter level (direct)
Stimulates CaSR gene transcription (indirect regulation of PTH)

40
Q

Vitamin D function (calcitriol)

A

Binds nuclear receptor - VDR
Inhibits PTH synthesis at promoter level (direct)
Stimulates CaSR gene transcription (indirect regulation of PTH)

41
Q

Vitamin D renal function (calcitriol)

A

Binds nuclear receptor - VDR
Inhibits PTH synthesis at promoter level (direct)
Stimulates CaSR gene transcription (indirect regulation of PTH)

42
Q

Vitamin D bone function

A

Direct: increases Ca2+ mobilization from bone; increases osteoclast activity
Indirect: increases plasma Ca2+, promoting bone mineralization

43
Q

Vitamin D intestinal function

A

Increases transcellular Ca2+ absorption in duodenum; stimulates Pi reabsorption from small intestine

44
Q

Vitamin D intestinal function

A

Increases transcellular Ca2+ absorption in duodenum; stimulates Pi reabsorption from small intestine

45
Q

Common cause of hyperphospotemia

A

Traumatic crush injury

46
Q

Binds/transports Ca2+ in intestinal epithelial cells

A

Calbindin 9k

47
Q

Binds/transports Ca2+ in intestinal epithelial cells

A

Calbindin 9k

48
Q

Reduced bone density - mainly trabecular bone

A

Osteoporosis

49
Q

Hyperplasia carcinoma of parathyroid gland

A

Hyperparathyroidism

50
Q

Hypocalcemic tetany; Chvostek sign observed

A

Hypoparathryoidism

51
Q

Unmineralized bone due to Vitamin D deficiency

A

Rickets (children)

Osteomalacia (adults)

52
Q

Unmineralized bone due to Vitamin D deficiency

A

Rickets (children)

Osteomalacia (adults)

53
Q

Uses of calcitonin

A

Treatment of Paget disease

Function: inhibits osteoclast reabsorption and slows bone turnover (net → slows bone turnover)

FHB (15 decks)

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