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Clinical Chem 2 > parathyroid > Flashcards

parathyroid Flashcards

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1
Q

primary targets for PTH

A

bones, kidney and GI

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2
Q

how does PTH impact bone

A

mobilizes calcium from bone - increases bon resorption (calcium from bone to blood)

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3
Q

how does parathyroid detect lowering calcium

A

calcium sensing receptors (CSRs)

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4
Q

impact of PTH on kidney (3 general)

A
  • increases reabsorption of renal tubular calcium
  • increases phosphate excretion
  • enhance 1-hydroxylation of 25 hydroxy vitamin D
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5
Q

name the active metabolite of vitamin D

A

1,25-dihydroxyvitamin D (calcitriol)

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6
Q

action of 1,25-dihydroxyvitamin D (calcitriol)

A

active absorption of calcium in small intestine

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7
Q

describe general vitamin D

A
  • steroid hormone from cholesterol
  • two forms D3 and D2
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8
Q

vitamin D3

A
  • cholecalciferol
  • dietary source
  • more potent than D2
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9
Q

vitamin D2

A
  • ergocalciferol
  • rare
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10
Q

name the natural ligand of vitamin D receptor

A

1,25(OH)2D

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11
Q

list the vitamin D conversion steps that take place in the skin

A

7-dehydrocholesterol –(UVB radiation)–> vitamin D3

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12
Q

describe the steps of vitamin D conversion that take place in the liver

A

vitamin D3–(25-hydroxylase)–>25(OH)vitamin D

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13
Q

list the vitamin D conversion steps that take place in the kidney

A

25(OH)Vitamin D –(1-hydroxylase)-> 1,25(OH)2 vitamin D active metabolite

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14
Q

in what organ order does the vitamin D activation pathway follow

A

skin - vitamin D3
liver - 25(OH)vitamin D
kidney - 1,25(OH)vitamin D

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15
Q

vitamin D impact on phosphate

A

increases absorption (higher passive)

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16
Q

body response to high blood calcium

A
  • decrease bone resorption
  • increase urinary loss
  • decrease active vitamin D production = decrease GI absorption
17
Q

renal failure patients calcium impact

A
  • disturbed calcium and phosphate metabolism
  • can’t convert 25 to 1,25
  • failure to excrete phosphate in urine = hyperphosphatemia
18
Q

What does hyperphosphatemia cause

A
  • PTH and fibroblast growth factor 23 (FGF23)
  • FGF23 causes low active Vit D levels
  • hypocalcemia
19
Q

PTH levels in chronic renal failure

A

elevated

20
Q

describe bone turnover

A

coupled process of bone formation and breakdown for balanced formation

21
Q

define resorption

A

bone breakdown to release calcium

22
Q

bone formation markers

A
  • ALP
  • osteocalcin
  • procollagen N terminal
23
Q

bone resorption markers

A
  • hydroxyproline
  • N-teopeptide/C-telopeptide
  • pryridinium crosslink
  • TRAP
24
Q

describe cortical bone and trabecular bone

A
  • cortical -shaft
  • trabecular bone - honeycomb top
25
Q

describe primary hyperparathyroidism (PHPT)

A
  • hypercalcemia most common cause
  • key feature: autonomous overproduction of PTH from single gland
26
Q

diagnosis criteria for PHPT

A

elevated serum calcium and elevated PTH relateive to serum calcium

27
Q

biochemical findings in PHPT

A
  • hypercalcemia
  • hypophosphatemia
  • low-normal 25 and high-normal 1,25
  • elevated urinary calcium
  • metabolic hypercholeremia acidosis
  • elevated ALP
28
Q

common PTH assessments

A
  • sandwich ELISA
  • electrochemiluminescent
29
Q

PHPT important points

A
  • gradual progression
  • kidney stones (20-30%)
  • bone loss (cortical>trabecular)
  • surgery = treatment
  • single gland tumor is common
30
Q

secondary hyperparathyroidism

A
  • elevated PTH in response to hypocalcemia
  • transient PTH elevation
31
Q

biochemical findings in secondary hyperparathyroidism

A
  • low: blood Ca and P
  • increased: ALP
  • Vit D deficiancy or lack of Vit D effect
32
Q

name the difference between secondary and tertiary hyperparathyroidism

A

sustained hypercalcemia
Tertiary: sustained hyper
Secondary: transient

33
Q

familial hypocalciruis hypercalcemia

A

germline mutation causing benign hypercalcemia
- multiple family members impacted
- no end organ damage
- mild elevation of magnesium

34
Q

parathyroid hormone related protein (PTHrP)

A
  • structurally similar to PTH
  • leads to hypercalcemia since it acts as PTH
35
Q

difference between PTH and PTHrP

A

PTHrP can’t facilitate renal hydroxylation of 25-hydroxyvitamin D to active vitamin D

36
Q

rickets

A

osteomalacia in children
- abnormal mineralization of bone
- diagnosed by PTH measurement
- genetic defect in Vit D metabolism (usually)

37
Q

osteomalacia

A

abnormal mineralization of bone
vitamin D deficiency

38
Q

osteoporosis

A

product of bone malformation or excessive resorption

Clinical Chem 2 (25 decks)

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