Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

4 - Y5 a Path lectures 2021/22 > ChemPath 1: Calcium Metabolism > Flashcards

ChemPath 1: Calcium Metabolism Flashcards

1
Q

Why must the calcium in blood be fixed?

A

nerves, muscles rely on Ca for depolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does Hypercalcaemia cause?

A
  • failure of depolarisation –
  • stones, bones, groans, moans + nephrogenic DI
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does Hypocalcaemia cause?

A
  • “trigger happy CNS” –
  • epilepsy (aberrant firing of nerves and muscles) –
  • CATS go numb
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the normal range of Ca in blood?

A
  • Normal Ca = 2.2 - 2.6mmol/l
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What % of calcium is in serum?

A

1%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where is the rest of the Calcium in the body?

A

complexed with phosphate in bones and teeth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What forms is the 1% of Ca in the serum in?

A
  • Free, ionised calcium, biologically active –> 50% à maintain at a fixed level
  • Protein-bound as albumin –> 40%
  • Complexed with citrate/phosphate –> 10%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens to the blood Ca levels if albumin is abnormal?

A
  • An abnormal albumin affects the free calcium (e.g. in sepsis)
  • If albumin is low…
    • Bound calcium will be low, but free calcium is normal
    • Corrected Ca refers to that (the corrected calcium can tell you what is wrong with albumin)
    • So, if albumin = 30 and total Ca = 2.2
    • Corrected Ca = 2.2 +(0.02 x 10) = 2.4mM
    • So, corrected Ca shows if the problem is albumin, and that ionised Ca will be normal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How might you overcome the abnormal Ca caused by abnormal albumin?

A
  • “Corrected ca” reported by labs
  • This compensates for albumin
  • Serum Ca + 0.02 x (40 – serum albumin (g/l))
  • In blood gas machines, ionised Ca can also be measured (around 1.1mmol/L)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is circulating Ca important for?

A
  • Important for normal nerve, muscle function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens in Chronic Ca deficiency?

A
  • loss in Ca from bone to maintain circulating Ca
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which organ detects hypoglycaemia?

A
  • Hypocalcaemia is detected by parathyroid gland
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the actions of PTH?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which are the 2 key hormones involved in Ca homeostasis?

A
  1. PTH
  2. Vitamin D (steroid hormone)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the 2 forms of vitamin D? What are they activated by?

A
  • D3 → animal product, from sunlight hitting skin → cholecalciferol
  • D2 → plants → ergocalciferol
  • both activated by 1-alpha hydroxylase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the structure of PTH

A

84 aa protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is vitamin D in the blood measured?

A
  • Measurement = 25-OH Vitamin D3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Where are the 2 forms of Vitamin D synthesised?

A
  • Vitamin D3 is synthesised in the skin – cholecalciferol
  • Vitamin D2 is a plant vitamin – ergocalciferol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Name the organs in which Vitamin D is synthesised/processed etc and describe what happens at each

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Are vitamin D3 and D2 active?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe what happens to whether Vitamin D is active (or not) as it is processed in the body

A
  1. (SKIN) D3 → animal product, from sunlight hitting skin → cholecalciferol;
    (INTAKE) D2 → plants → ergocalciferol
    = ACTIVE
  2. (LIVER) 25-hydroxylase –> 25-hydroxy-Vitamin D3
    = INACTIVE
  3. (KIDNEY) 1α hydroxylase –> 1,25-dihydroxy Vitamin D3
    = ACTIVE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Which enzyme hydoxylates Vitamin D3 and D2 in the liver?

A

25 hydroxylase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Which enzyme hydroxylates 25-hydroxy-vitamin D3 in the kidneys?

A

1α hydroxylase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Where can 1α hydroxylase also be expressed (other than the kidneys)?

A
  • Rarely, this enzyme is expressed in lung cells of sarcoid tissue
  • Sarcoid = causes hypercalcemia (seasonal) – summer hypercalcemia
  • In sunlight, calcium goes up (more vitamin D activation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is another name for 25-hydroxy-Vitamin D3?

A

calcidiol (prior to 1a hydroxylation in the kidneys)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is another name for 1,25-dihydroxy-Vitamin D3?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the role of Role of 1,25 (OH)2 Vitamin D (Calcitriol)?

A
  • Intestinal Ca2+ absorption and intestinal phosphate absorption
  • Critical for bone formation (with osteoblasts)
  • Other physiological effects
    • Vitamin D receptor controls many genes – cell proliferation, immune system
    • Vitamin D deficiency associated with cancer, autoimmune disease, metabolic syndrome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the cause of rickets/osteomalacia?

A
  • Vitamin D deficiency
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the cause of osteoporosis?

A

lack of oestrogen

30
Q

What does Vit D deficiency cause?

A
  • Defective bone mineralisation
  • Childhood → rickets; Adults → osteomalacia
31
Q

Describe the epidemiology of Vitamin D deficiency in the UK

A
  • More than 50% adults have insufficient vitamin D
  • 16% have severe deficiency during winter and spring
32
Q

What are the risk factors for Vit D deficiency?

A
  • Lack of sunlight exposure
  • Dietary
  • Dark skin
  • Malabsorption
33
Q

What are the clinical features of Osteomalacia?

A
  • Bone and muscle pain
  • Increase fracture risk
  • Looser’s zones (pseudo fractures)
34
Q

What is the biochemistry seen in osteomalacia?

A

Bio-chem →

  • low Ca2+ and phosphate
  • raised ALP
35
Q

What are the clinical feautures of rickets?

A
  • Bowed legs
  • Costochondral swelling
  • Widened epiphyses at the wrists
  • Myopathy (weak muscles)
36
Q

What is the cause of the features of osteomalacia?

A

lack of Ca

37
Q

What are the clinical features of osteomalacia?

A
  • Bone is demineralised
  • Caused by vitamin D deficiency
  • Renal failure
  • Anticonvulsants induce breakdown of Vitamin D (phenytoin)
  • Lack of sunlight
  • Chappatis – phytic acid (cause osteomalacia)
38
Q

What is the first clinical feature of osteoporosis?

A
  • pathological fracture (asymptomatic until then)
  • (more common as you age, bone lost slowly after 20)
39
Q

What is the pathogenesis of osteoporosis?

A
  • Loss of bone mass, (Reduction in bone density)
  • but residual bone normal in structure (normal mineralisation)
40
Q

What happens to the biochemistry in osteoporosis?

A

all normal

  • Osteoporosis has bone loss but with a normal calcium
41
Q

How is osteoporosis diagnosed?

A
  • DEXA scan (Dual energy X-ray absorptiometry):
42
Q

Where are the common sites of fractures in osteoporosis?

A
  • Hip (femoral neck)
  • lumbar spine
43
Q

Explain T scores and Z scores

A
  • T score – SD from mean of young healthy population – determine fracture (#) risk
  • Z score – SD from mean of age-matched control – identify accelerated bone loss in younger people
44
Q

What are the diagnostic values for osteoporosis and osteopenia? (T scores)

A
  • Osteoporosis – T score
  • Osteopenia – T score -1 and -2.5
45
Q

What is the Tx for osteoporosis?

A
  • Lifestyle
    • Weight bearing exercise
    • Stop smoking
    • Reduce ETOH
  • Drugs
    • Vitamin D/Ca
    • Bisphosphonates (alendronate) – decrease bone resorption – osteonecrosis of jaw
    • Teriparatide – PTH derivative – anabolic
    • Strontium – anabolic + anti-resorptive
    • Oestrogens – HRT
    • SERMs (oestrogen-like drug) – raloxifene (like Tamoxifen)
    • Denosumab – biologic anti-RANK-L antibody
46
Q

What are the symptoms of hypercalcaemia?

A
  • Polyuria or polydipsia
  • Bones
  • Stones
  • Abdo - constipation
  • Neuro – confusion, seizures, coma
  • Unlikely unless Ca >3mmol/L (2.2-2.6)

Overlap with symptoms of hyperPTH

47
Q

What qs must be asked when bloods come back as hypercalcaemia?

A
  • First Q: is it a genuine result (repeat)
  • 2nd Q: what is the PTH?
48
Q

What can a high albumin in bloods mean in hypercalcaemia?

A
  • High albumin = artificially elevated Ca
49
Q

What is secondary hyperparathyroidism associated with?

A

2nd HPT is associated with a LOW calcium due to low vitamin D

50
Q

What is the commonest cause of hypercalcaemia?

A

Primary Hyperparathyroidism

51
Q

What are some causes of primary hyperparathyroidism?

A
  • Parathyroid adenoma (80%)
  • Hyperplasia
    • associated with MEN1, 2a
  • Malignancy of the parathyroid gland (carcinoma)
52
Q

sWhat blood results will be seen in hypercalcaemia due to primary hyperparathyroidism?

A
  • High serum Ca
  • Low serum phosphate
  • High PTH - inappropriate
  • High urine Ca due to hypercalcemia
53
Q

What blood results will be seen in hypercalcaemia due to malignancy elsewhere in the body?

A
  • High serum Ca
  • Low serum phosphate
  • Low serum PTH – appropriate
54
Q

What different presentations may a patient with primary hyperparathyroidism present with?

A

bones, urinary stones, abdo moans, psychiatric groans

55
Q

Which organs have Ca-sensing receptors?

A
  • Parathyroid – regulate PTH
  • Renal – influences Ca resorption – PTH independent
56
Q

What is Familial hypocalciuric hypercalcemia?

A
  • Calcium Sensing Receptors mutation
  • Reduced sensitivity to calcium
  • Higher set point for PTH release
57
Q

What bloods and urine results are seen in Familial hypocalciuric hypercalcemia?

A
  • Mild hypercalcaemia
  • Reduced urine Ca
58
Q

What are the 3 causes of hypercalcaemia seen in malignancy?

A
  1. Humoral hypercalcaemia of malignancy – squamous cell lung cancer
    1. PTHrP released
  2. Bone mets – e.g. in breast ca
    1. Local bone osteolysis
  3. Haematological malignancy – myeloma
    1. Cytokines
59
Q

What are some other causes of non-PTH driven hypercalcaemia ?

A
  • Sarcoidosis – non renal 1α hydroxylation
  • Thyrotoxicosis – thyroxine leads to bone resorption
  • Hypoadrenalism – renal Ca transport
  • Thiazide diuretics – renal Ca transport
  • Excess vitamin D – sunbeds
60
Q

What is the Tx for hypercalcaemia?

A
  • FLUIDS (0.9% saline, 1L/hour and reassess)
  • Treat underlying cause
  • Cinacalcet acid – activates Ca sensing receptors
61
Q

What are the signs & symptoms of hypocalcaemia?

A
  • Neuromuscular excitability –> Chvostek’s sign (face), Trousseau’s sign, hyperreflexia
  • Convulsions
62
Q

What must be done when diagnosing hypocalcaemia?

A
  • 1st –> repeat bloods and adjust for albumin (as the albumin can bind ionised calcium) - i.e. is the hypocalcaemia a genuine result?
  • 2nd –> what is the PTH?
63
Q

What are the non-PTH driven causes of hypocalcaemia?

A
64
Q

What are the PTH-driven (due to low PTH) causes of hypocalcaemia?

A
65
Q

Which has the lowest calcium out of:

  • primary HPT
  • secondary HPT
  • osteoporosis
  • Paget’s
  • breast cancer
A

secondary HPT

66
Q

What is Paget’s disease?

A

focal disorder of bone remodelling

67
Q

What are the signs and symptoms of Paget’s disease?

A
  • Bone pain
  • Warmth
  • Cardiac failure
  • Deformity
  • Fracture
  • Malignancy
  • Compression (blindness, deafness)

Commonly affected bones: Pelvis, femur, skull and tibia

68
Q

What are the bloods seen in Paget’s disease?

A
  • Elevated alkaline phosphatase
    • Ca and PO4 are NORMAL as…
    • Osteoclasts and blasts are both active together
69
Q

What imaging is conducted in ?Paget’s disease?

A
  • Nuclear med scan / XR
70
Q

What is the Tx of Paget’s disease?

A
  • Bisphosphonates for pain
71
Q

What:

  • Ca
  • phosphate
  • PTH
  • Alk Phos
  • Vit D

is seen in the following conditions?

A
72
Q

What are some other metabolic bone disorders?

A
  • renal osteodystrophy
    • due to secondary HPT + retention of aluminuim from dialysis fluid
  • osteistis cysitica
    • in primary HPT, loss of cortical bone –> fracture risk

both are quite rare due to modern Tx of underlying cause

4 - Y5 a Path lectures 2021/22 (37 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions