L.12 Bone Metabolism Flashcards
1
Q
What is the most abundant mineral in the body?
A
Calcium
Calcium is essential for various physiological processes.
2
Q
What are minerals?
A
Inorganic substances that are essential for the body
Examples include calcium, phosphorus, magnesium, iron, and zinc.
3
Q
What percentage of calcium is stored in the bones and teeth?
A
99%
The remaining 1% is found in the blood and soft tissues.
4
Q
What is a key function of calcium in muscle cells?
A
Triggers muscle contraction
Calcium ions are released in response to a nerve impulse.
5
Q
How do calcium ions contribute to nerve function?
A
Involved in the release of neurotransmitters
This allows nerve cells to communicate with each other.
6
Q
What role does calcium play in blood clotting?
A
Involved in the clotting cascade
Calcium is required by factors VII, IX, X, and prothrombin.
7
Q
What is calcium’s role in bone formation?
A
Required for the mineralisation of bone
Bone is made up of calcium phosphate crystals (hydroxyapatite).
8
Q
What is the recommended daily calcium intake?
A
1000mg/day
This is the amount suggested for maintaining healthy calcium levels.
9
Q
How much calcium is absorbed daily?
A
350mg/day
Indicates the efficiency of calcium absorption in the body.
10
Q
How much calcium is lost daily in feces?
A
900mg/day
This loss affects overall calcium balance.
11
Q
What is the total amount of calcium in bones?
A
1000000mg
Bones serve as a major reservoir for calcium.
12
Q
What is the amount of calcium in cells?
A
13000mg
Cells contain a smaller portion of the body’s total calcium.
13
Q
How much calcium is found in extracellular fluid?
A
1300mg
Extracellular fluid is critical for various physiological functions.
14
Q
What is the rapidly exchangeable pool of calcium?
A
1% of total body calcium
This pool is important for maintaining blood calcium levels.
15
Q
What is the role of the rapidly exchangeable pool of calcium?
A
Buffers changes in blood calcium levels
It maintains calcium homeostasis in the body.
16
Q
What is the balance between bone resorption and bone formation?
A
Essential for maintaining calcium levels
This balance impacts overall bone health.
17
Q
What percentage of plasma calcium is free ionised calcium?
A
50%
Reference range = 1.20 - 1.37 mmol/L
18
Q
What is the biologically active form of calcium in plasma?
A
Free ionised calcium
19
Q
What percentage of plasma calcium is protein-bound?
A
40%
20
Q
What percentage of plasma calcium is complexed calcium?
A
10%
21
Q
What type of sample container should be used for plasma calcium measurement?
A
Green cap
22
Q
What type of sample container should be used for serum calcium measurement?
A
Red cap
23
Q
Which sample container should NOT be used for calcium measurement?
A
Purple cap with EDTA anticoagulant
24
Q
What method uses the cresolphthalein complexone (CPC) for measuring calcium?
A
Spectrophotometric method
25
What is the principle of the CPC method?
CPC forms a red-purple complex with calcium ions
26
What is the absorbance range for the CPC method?
570-580nm
27
What can interfere with the CPC method reaction?
Magnesium
28
What agent can be added to the CPC method to remove magnesium?
8-hydroxyquinoline
29
What is the principle of the Direct Ion-selective electrode (ISE) method?
ISE measures the activity of free calcium ions in the sample
30
What is the reference range for calcium measured by ISE?
1.20 - 1.37 mmol/L
31
What are the advantages of the ISE method?
Fast, accurate, and requires small sample volume
32
What is corrected calcium used for?
To adjust the total calcium concentration for changes in albumin levels
33
What is the main protein that binds calcium in the blood?
Albumin
34
If albumin levels are low, what happens to the total calcium concentration?
It will be low
35
What are the three key regulators of calcium in the body?
Parathyroid hormone (PTH), Calcitonin, Vitamin D
36
Where are the parathyroid glands located?
On the posterior surface of the thyroid gland in the neck
37
What triggers the release of PTH?
Low blood calcium levels
38
What is the structure of PTH?
84 amino acid peptide hormone
39
How is PTH stored?
In secretory granules in the parathyroid glands
40
What is the half-life of PTH in the blood?
5-10 minutes
41
How is PTH degraded?
Rapidly by the liver and kidney
42
What is the active form of vitamin D?
1,25-dihydroxycholecalciferol (calcitriol)
43
What stimulates the production of calcitriol in the kidneys?
PTH
44
What enzyme is involved in the production of calcitriol?
1-alpha hydroxylase
45
Name one effect of Vitamin D on calcium.
Increases calcium absorption in the intestines
46
How does Vitamin D affect calcium reabsorption?
Increases calcium reabsorption in the kidneys
47
What is the relationship between calcitriol and PTH?
Calcitriol inhibits the production of calcitriol (antagonist of PTH)
48
What cells secrete calcitonin?
Parafollicular cells (C cells) of the thyroid gland
49
What is the role of calcitonin in relation to blood calcium levels?
Decreases blood calcium levels
50
How does PTH affect blood calcium levels?
Increases blood calcium levels
51
True or False: Calcitonin plays a greater role in calcium homeostasis compared to PTH and vitamin D.
False
52
Fill in the blank: PTH is released in response to _____ blood calcium levels.
low
53
Fill in the blank: The lesser role in calcium homeostasis is attributed to _____ compared to PTH and vitamin D.
calcitonin
54
What is hypocalcaemia?
Serum/plasma calcium levels below the reference range (< 2.2 mmol/L)
## Footnote
Hypocalcaemia can result from various physiological or pathological conditions.
55
What are the three main causes of hypocalcaemia?
* ↓ GI absorption
* ↑ renal loss
* ↓ bone loss
## Footnote
These causes can lead to a decrease in serum calcium levels.
56
What are some artefactual causes of hypocalcaemia?
* ↓ albumin levels
* EDTA contamination
## Footnote
Artefactual causes can lead to misleading low serum calcium readings.
57
What are the neurological symptoms of hypocalcaemia?
* Tetany
* Seizures
* Paraesthesia
* Tingling
## Footnote
These symptoms arise due to excitability of nerves and muscles from low calcium levels.
58
What cardiovascular symptoms are associated with hypocalcaemia?
* Arrhythmias
* ECG changes
## Footnote
Cardiac symptoms can be serious and require immediate medical attention.
59
What is Chvostek’s sign?
Facial muscle spasm in response to tapping the facial nerve
## Footnote
This sign is indicative of hypocalcaemia.
60
What long-term condition can develop from hypocalcaemia?
Cataracts
## Footnote
Chronic hypocalcaemia can lead to various complications including cataracts.
61
What is the first line treatment for hypocalcaemia?
Oral calcium supplements
## Footnote
Supplementation is essential to correct calcium deficiency.
62
What supplements are recommended alongside oral calcium for hypocalcaemia treatment?
Vitamin D supplements
## Footnote
Vitamin D is crucial for calcium absorption.
63
What underlying causes should be treated in hypocalcaemia?
Identify and address the specific cause of calcium deficiency
## Footnote
Treating the underlying issue is essential for effective management.
64
How does vitamin D deficiency affect calcium absorption?
Vitamin D is required for calcium absorption in the intestines
## Footnote
Without adequate vitamin D, calcium absorption is significantly reduced.
65
What conditions can lead to malabsorption of calcium?
* Coeliac disease
* Crohn’s disease
* Short bowel syndrome
## Footnote
These gastrointestinal disorders can impede calcium absorption.
66
What can reduced calcium absorption lead to in children and adults?
* Osteomalacia (in adults)
* Rickets (in children)
## Footnote
Both conditions are characterized by weakened bones due to inadequate mineralization.
67
What is osteomalacia?
Softening of the bones due to defective mineralisation
## Footnote
Osteomalacia is the adult form of the condition, while rickets is the childhood form.
68
What is the main cause of osteomalacia and rickets?
Vitamin D deficiency
## Footnote
Fortification of foods with vitamin D has reduced the incidence of these conditions.
69
What are the symptoms of osteomalacia and rickets?
Bone pain, bone deformities, and fractures.
70
What happens in renal failure concerning vitamin D?
Cannot hydroxylate vitamin D to its active form
## Footnote
This leads to reduced calcium reabsorption in the kidneys.
71
What effect does renal failure have on calcium absorption?
Reduced GI absorption of calcium due to vitamin D deficiency.
72
What is the effect of vitamin D deficiency on bone resorption?
Reduced bone resorption.
73
What may happen to a diseased kidney's response to PTH?
It may not respond to PTH.
74
What can occur due to overproduction of PTH by the parathyroid gland?
Stimulates bone resorption leading to mineral bone disease of CKD.
75
What is hypoparathyroidism?
Parathyroid glands do not produce enough PTH.
76
What is the consequence of insufficient PTH production?
PTH no longer stimulates bone resorption.
77
What are some causes of hypoparathyroidism?
* Autoimmune destruction of the parathyroid glands
* Surgical removal of the parathyroid glands (parathyroidectomy)
* Congenital hypoparathyroidism
* Idiopathic (unknown cause)
78
What is hungry bone syndrome?
Rapid uptake of calcium into the bones after parathyroidectomy.
79
What is a potential consequence of hungry bone syndrome?
Leads to hypocalcaemia.
80
What is hypercalcaemia?
Serum/plasma calcium levels above the reference range (> 2.5 mmol/L)
## Footnote
Hypercalcaemia can result from various factors including increased absorption, decreased renal loss, and increased bone loss.
81
What are the three main causes of hypercalcaemia?
* ↑ GI absorption
* ↓ renal loss
* ↑ bone loss
## Footnote
Hypercalcaemia can also be caused by artefactual factors.
82
What are some artefactual causes of hypercalcaemia?
↑ albumin levels
## Footnote
High albumin levels can falsely elevate serum calcium readings.
83
What are the neurological symptoms of hypercalcaemia?
* Confusion
* Lethargy
* Coma
## Footnote
Neurological symptoms can vary in severity based on calcium levels.
84
What cardiovascular symptoms are associated with hypercalcaemia?
* Arrhythmias
* ECG changes
## Footnote
These symptoms can indicate serious complications of hypercalcaemia.
85
What gastrointestinal symptoms are typical in hypercalcaemia?
* Constipation
* Anorexia
* Nausea
## Footnote
GI symptoms can significantly affect patient quality of life.
86
What renal symptoms can occur due to hypercalcaemia?
* Polyuria
* Polydipsia
## Footnote
These symptoms are due to the effects of calcium on kidney function.
87
What is the initial treatment for hypercalcaemia?
* IV fluids
* Bisphosphonates
* Treat underlying cause
## Footnote
Urgent treatment is required if calcium levels are ≥ 3.5 mmol/L.
88
What role does vitamin D play in hypercalcaemia?
Vitamin D increases calcium absorption in the intestines
## Footnote
Excessive vitamin D intake can lead to hypercalcaemia.
89
What granulomatous diseases can cause hypercalcaemia?
* Sarcoidosis
* Tuberculosis
## Footnote
Granulomas in these diseases increase production of 1,25-dihydroxycholecalciferol.
90
How do thiazide diuretics contribute to hypercalcaemia?
Thiazide diuretics reduce calcium excretion in the kidneys
## Footnote
This action leads to elevated serum calcium levels.
91
What is milk-alkali syndrome?
Excessive intake of calcium and alkali (e.g. milk and antacids)
## Footnote
Alkalosis in this syndrome reduces the kidney's ability to excrete calcium.
92
True or False: Increased calcium binding to albumin due to alkalosis can contribute to hypercalcaemia.
True
## Footnote
This mechanism is part of the milk-alkali syndrome.
93
What condition is characterized by excessive production of PTH by the parathyroid glands?
Hyperparathyroidism
## Footnote
Hyperparathyroidism leads to increased bone resorption.
94
What effect does PTH have on bone?
Stimulates bone resorption
## Footnote
This process results in increased bone loss.
95
What condition is associated with elevated thyroid hormone levels and increased bone turnover?
Thyrotoxicosis
## Footnote
Thyrotoxicosis can lead to hypercalcaemia.
96
Which cancers can cause increased bone loss through the production of PTH-related protein?
Malignancy
## Footnote
Examples include multiple myeloma, breast cancer, and lung cancer.
97
What is the most common cause of acute hypercalcaemia?
PTH-related protein (PTHrP) production by tumors
## Footnote
PTHrP mimics the action of PTH.
98
What is one common cause of decreased bone formation?
Immobilisation
## Footnote
Examples include bed rest and paralysis.
99
List the components of the Bone Profile.
Total calcium, Phosphate, Alkaline phosphatase, Albumin
## Footnote
Corrected calcium is derived from total calcium and albumin levels.
100
What does alkaline phosphatase (ALP) indicate in bone health?
Marker of bone formation
## Footnote
ALP may be elevated in bone disease.
101
What is the reference range for phosphate levels in the blood?
0.8 - 1.4 mmol/L
## Footnote
Phosphate is the second most abundant mineral in the body.
102
How does PTH affect calcium and phosphate levels?
Increases calcium levels and decreases phosphate levels
## Footnote
This reflects a reciprocal relationship in blood.
103
What additional test can help with the differential diagnosis of hypercalcaemia?
PTH
## Footnote
PTH testing methods include immunoassay.
104
What role does Vitamin D play in diagnosing calcium disorders?
Helps with the differential diagnosis of hypercalcaemia and hypocalcaemia
## Footnote
Testing methods include LC-MS/MS, HPLC, and immunoassay.
105
What is the reference range for Vitamin D levels?
50 – 125 nmol/L
## Footnote
Vitamin D is crucial for calcium metabolism.
