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2 - Calcium Pathology Flashcards

(75 cards)

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1
Q

Hyperparathyroidism is a condition of what?

A

Excess PTH secretion

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2
Q

What two types of hyperparathyroidism are there?

A

Primary - within parathyroid gland

Secondary - elsewhere i.e. Chronic renal failure / rickets

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3
Q

What is a common cause of primary hyperthyroidism?

A

Monoclonal parathyroid adenoma (hyperplasia)

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4
Q

What two serum findings result from primary hyperparathyroidism?

A

1) Hypercalcaemia

2) HYPOphosphataemia

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5
Q

What are 2 complications of primary hyperparathyroidism? (bone/kidney)

A

Bone demineralisation - loss of calcium and phosphate.

Renal calculi from hypercalciuria - concentrations get so high it comes out of solution.

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6
Q

What are the most common type of calcium kidney stones?

A

Calcium oxalate

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7
Q

What is a complication of chronic bone demineralisation?

A

Multiple bone cysts

osteitis fibrosa cystica

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8
Q

What are 3 genetic causes of primary HPT?

A

1) Vitamin-D receptor mutation
2) MEN1 mutation
3) Over-expression of cyclin D1

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9
Q

What’s the pathophysiology of a vitamin-D receptor mutation leading to Primary HPT?

A

Vitamin D-R provides negative feedback to parathyroid gland, inhibiting gene expression of PTH.

Mutation = loss of -ve feedback.

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10
Q

What’s the pathophysiology of MEN1 mutation causing primary HPT?

A

MEN1 is a tumour suppressor gene. Mutation results in neoplasia.

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11
Q

What’s the pathophysiology of cyclin D1 over-expression causing primary HPT?

A

Cyclin D1 is a cell-cycle regulator.

Overexpression favours cell division = sporadic parathyroid adenoma.

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12
Q

What other symptoms occurs with hyperparathyroidism?

A

‘Stones, bones, abdominal groans and psychic moans’

Muscle weakness, depression, GI upset, lethargy, aches.

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13
Q

What is tetany?

A

Muscular spasms, caused by a deficiency in calcium (Parathyroid dysfunction)

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14
Q

What is the treatment for primary HPT?

A

Surgery - parathyroidectomy

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15
Q

What is the main complication of a parathyroidectomy?

A

Nephrolithiasis

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16
Q

How do you best avoid nephrolithiasis following a parathyroidectomy?

A

Hydration

Moderate calcium intake

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17
Q

What scan is used to detect parathyroid tumours?

A

Sestamibi

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18
Q

What radioactive isotope is used in the sestamibi scan?

A

Technetium 99

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19
Q

What is the full name of the modern parathyroidectomy?

A

Minimally invasive radio-guided parathyroidectomy (MIRP)

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20
Q

During the MIRP, how does the surgeon confirm excised tissue is a tumour and that they’ve got it all?

A

Radiation-sensitive probe can detect the presence of Technetium 99.

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21
Q

What two pathologies occur in the kidney that can augment secondary hyperparathyroidism?

A

1) Increase phosphate reabsorption (inability to excrete)

2) Decreased 1alpha hydroxylation (less vitamin D)

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22
Q

What 4 factors (2 direct, 2 indirect) therefore, increase the level of PTH secretion?

A

1) High plasma phosphate
1b) Low free calcium
2) Low vitamin D
2b) Decrease calcium GUT absorption

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23
Q

Chronic renal failure results in what area of the kidney being unresponsive to PTH levels?

A

Proximal convoluted tubule

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24
Q

In the non-affected PCT cells, what two proteins are affected by PTH?

A

1) PTH inhibits the NaPi transporter

2) PTH increases activity of 1-alpha-OHase

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25
In chronic renal failure, what three consequences occur in the PCT as a result of a lack of response to PTH?
1) Hyperphosphataemia 2) Hypocalcaemia 3) Acidosis
26
What 3 pharmaceutical agents can be used for secondary hyperthyroidism?
1) Vitamin D supplementation 2) Calcimimetics 3) Phosphate binders
27
How does Vitamin D work in the context of secondary HPT?
Increases serum calcium and phosphate levels.
28
What are the issues with using Vitamin D as a treatment of secondary HPT?
Increases phosphate - already high because kidneys can't get rid of it. Slow onset. Does nothing to reverse hyperplasia.
29
Give an example of a calcimimetic?
Cinacalcet
30
How often is cinacalcet taken?
1x daily
31
How does it work?
Positive allosteric modulators - activating the calcium receptor to inhibit PTH secretion. (chemical parathyroidectomy)
32
Which cohort of patients can receive calcimimetics? As a result of what risk?
Dialysis patients Risk of hypocalcaemia
33
Which two medications for secondary HPT are usually combined together? Why?
Vit D + Cinacalcet | vitamin D sustains calcium levels that cinacalcet drops
34
Give one example of a phosphate binder?
Renagel
35
How do phosphate binders work?
They bind to phosphate within the GI tract and stop its uptake - decreasing total PTH secretion.
36
What are the two clinical signs of HYPOcalcaemia?
Chvostek's sign Trousseaus sign
37
What is Chvostek's sign?
Muscular tremor elicited by tapping the facial nerve resulting in mouth spasm.
38
What is Trousseau's sign?
Hand contortion when taking blood pressure
39
What is Vitamin D-dependent Rickets Type 1?
An issue in vitamin D synthesis.
40
What is an example of an affected enzyme in the vitamin D pathway in VDDR1?
1-alpha hydroxylase
41
Where is 1-alpha-hydroxylase found?
Proximal tubule of the nephron
42
What is the pathophysiology of rickets?
Growth occuring, but long bone strength is poor - gravity takes its effect by bowing on the femur.
43
What is the definition of osteoporosis?
Bone mineral density of >2.5 S.D. below healthy controls.
44
What is the underlying cause of osteoporosis?
Imbalance of bone remodelling. Increase resorption, decrease formation.
45
What is osteopenia?
<2.5 S.D. below health controls - en route to osteoporosis.
46
What two changes occur from osteoporosis?
1) Reduced bone mass | 2) Microarchitectural deterioration
47
Which cohort is the most common to get osteoporosis?
Menopausal women
48
Which bones are most commonly fractured in osteoporosis?
Hips, pelvis, spine, wrists, shoulder.
49
In women, losing oestrogen has what effect on osteoclasts and osteoblasts?
Increase osteoblast apoptosis. Decrease osteoclast apoptosis.
50
Epidemiology of osteoporosis: - Prevalence (women / men) - Cost to NHS
Over 50: Men: 1/12 Women: 1/3 £2 billion / year
51
What two factors determine adult bone health?
1) Peak bone mass (puberty) | 2) Rate of bone loss
52
How do estrogens maintain bone mineral density - what do they bind to ?
ERalpha (ERbeta?) on osteoblasts
53
K/o studies of ERalpha have what effect on bone?
Decreases BMD.
54
Ovarectomy also results in what effect on bone?
Decreases BMD
55
What pharmaceutical agents can be used for post-menopausal women who haven't had a fracture?
Bisphosphonates Strontium ranelate Raloxifene
56
What hormone, in men, in linked more closely to bone demineralisation?
Oestrogen (not testosterone)
57
What pharmaceutical agents can be used for post-menopausal women that have had a fracture?
Bisphosphonates Strontium ranelate Raloxifene + Teriparatide
58
How do bisphosphonates work?
Inhibit osteoblast action - slowing bone loss.
59
What needs to be done after taking bisphosphonates?
Sit upright for 30 mins - causes heartburn.
60
What class of drug is raloxifene?
Selective estrogen-receptor modulator. (SERM)
61
What does teriparatide do? Who's it given to?
Drives bone formation Post-menopausal women with previous fracture.
62
Loss of function calcium-receptor mutations results in what shift on the calcium-PTH curve?
Rightward shift. | i.e. more calcium is required to elicit the same amount of suppression
63
What effect do loss-of-function calcium receptor mutations have on PTH levels?
Increased PTH levels (because less suppression)
64
What are two genetic types of calcium-receptor mutations?
1) Heterozygous | 2) Homozygous
65
A heterozygous calcium-receptor mutation is also called what?
Familial hypercalcaemia hypocalciuria
66
What is a homozygous calcium-receptor mutation called?
Neonatal severe hyperparathyroidsm
67
Familial hypercalcaemia hypocalciuria presents like what other condition? What's the difference?
Primary hyperparathyroidism Hypocalciuria (in Primary HPT, you get hypercalciuria)
68
What is the role of the calcium receptor in the nephron?
Reduce calcium reuptake
69
In FHH, what change occurs in the nephron?
Becomes less sensitive to calcium, so begins to reabsorb it
70
What two effects does FHH have then?
1) Increased PTH secretion because CaR not inhibiting. | 2) Increased Ca reabsorption because less sensitive to high concentrations.
71
What finding after a parathyroidectomy would make you think FHH?
Persistent hypercalcaemia.
72
what pharmacological agent is used to treat FHH?
Calcimimetics (reintroduce calcium sensitivity)
73
What is the treatment for neonatal severe hyperparathyroidism?
Early PTX Lifelong calcium + vitamin D supplementation.
74
What is a gain of function CaR mutation disease called?
Autosomal dominant hypocalcaemia
75
Why should you NOT given vitamin D supplements to ADH patients?
Increases calcium Hypercalciuria = Kidney stones / nephrogenic diabetes insipidus

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