LMP301 Lecture 11: Calcium, Vit D, Parathyroid Flashcards
Calcium, Vit D, parathyroid (90 cards)
1
Q
Where is calcium excreted?
A
- intestines (poop)
- kidneys
2
Q
Which hormones regulate calcium homeostatsis?
A
- parathyroid hormone
- 1,25 (OH)2 vit D
- calcitonin
3
Q
What stimulates PTH release?
A
low Ca++
4
Q
effect of PTH on bone
A
reabsorption (break down)
5
Q
effect of PTH on kidney
A
- Ca++ reabsorption
- P secretion
- incr. 1-OH’ase
- incr. 1,25 (OH)2 vit D
6
Q
Where does PTH act on?
A
- bones
- kidneys
7
Q
How do we get to the active form of 1,25 (OH)2 vit D?
A
- pro-vitamin D –(UV)–> vit D
- vit D –(25-OH’ase)–> 25-(OH)D3
- 25-(OH)D3 –(1a-OH’ase)–> 1,25-(OH)2D3
8
Q
Where can 25-OH’ase be found?
A
liver
9
Q
where can 1a-OH’ase be found?
A
many tissues, including kidneys, pancreas, colon, prostate, breasts…
10
Q
The active 1,25 (OH)2 vit D can be converted into the inactive…
A
1,24,25-(OH)3D3
11
Q
25 OH vit D can be converted into ____ by ____ (not the reaction to make 1,25-(OH)2D3)
A
24,25-(OH)2D3
24-OH’ase
12
Q
Sources of vit D3
A
- supplement
- sunlight on skin
- milk
- salmon
13
Q
function of 1,25-(OH)2D3 at pancreas, colon, prostate, breasts…
A
regulate cell growth (prevent cancer)
Prevent autoimmune diseases
14
Q
function of 1,25-(OH)2D3 at kidneys
A
prevent autoimmune diseases
maintain calcium homoeostasis (muscle & bone health)
15
Q
Where does 1,25-(OH)2D3 act on?
A
- intestines
- bones
- parathyroid gland
16
Q
effect of 1,25-(OH)2D3 on intestines
A
- increase Ca absorption
- incr P absorption
17
Q
Overall effect of 1,25-(OH)2D3
A
raise blood Ca++ levels
18
Q
effect of 1,25-(OH)2D3 on bone
A
increase reabsoprtion
19
Q
effect of 1,25-(OH)2D3 on parathyroid gland
A
decrease PTH
20
Q
Feedback of 1,25-(OH)2D3
A
- inhibit its own synthesis
- promotes its own breakdown
21
Q
1,25-(OH)2D3 is bound to ___ when in circulation
A
vit D binding protein
22
Q
receptor for 1,25-(OH)2D3
A
nuclear vit D receptor
23
Q
calcitonin is secreted by…
A
parafollicular / C cells of thyroid gland
24
Q
Secretion of calcitonin is stimulated by…
A
- high Ca
- GI hormones
25
Effect of calcitonin
- lower serum CA
- lower serum P
- stops bone reabsorption
26
Calcitonin is used as treatment for which bone diseases?
- post-menopausal osteoporosis
| - Paget's disease
27
Calcitonin is a tumour marker for...
medullary thyroid carcinoma (tumor of the C cells in thyroid gland)
28
Tetany is a symptom of...
hypocalcemia
29
Tetany
flexed wrist & ankle joint, muscle twitching, cramps
30
Hypocalcemia is usually present with...
neuromuscular hyperexcitability (tetany, Trousseau's sign)
31
Hypercalcemia is usually present with...
reduced neuromuscular excitability (fatigue, weakness, depression)
32
Hypercalcemia may induce...
ADH resistance = nephrogenic diabetes
- thirst
- polydipsia
- polyuria
33
hypercalcemia may cause ___ because of hypercalciuria and Ca buildup in the kidney
kidney stones
34
causes of hypocalcemia
- hypoparathyroidism
- pseudohypoparathyroidism
- magnesium deficiency
- renal failure
- vit D deficiency
35
hypoparathyroidism
parathyroid can't produce PTH
36
pseudohypoparathyroidism
high PTH
low Ca++
PTH resistance
37
magnesium deficiency contributing to hypocalcemia
Mg affects secretion of PTH
| high Mg = more PTH secretion
38
Why might renal failure cause hypocalcemia
- Retain P, so Ca++ is secreted
| - 1,25-(OH)2D3 deficiency
39
causes of vit D deficiency
- diet
- lack of sun
- can't absorb
- chronic liver disease
- chronic renal disease
- vit D dependent rickets
40
what are the Ca and PTH levels in renal failure and vit D deficiency?
- low Ca
- (in response) high PTH
This is secondary hypoparathyrodism
41
What are the causes of secondary hyperpaarathyrodism?
- renal failure
| - vit D deficiency
42
3 ways which hypercalcemia may happen
1. intestine absorption
2. bone reabsorption
3. renal reabsorption
43
Causes of hypercalcemia
- problem at parathyroid gland
- malignancies
- milk-alkali syndrome
- increased 1-OH'ase activity
- FHH
44
FHH
familial hypocalciuric hypercalcemia
- mutations of calcium sensing receptor in parathyroid gland
- autosomal dominant
- not severe, asymptomatic
45
FHH can be mistakenly diagnosed as...
hyperparathyroidism
46
Some cancers that may cause hypercalcemia may secrete...
PTHrP (related protein)
47
milk-alkali syndrome
take too much antacid
- increase bicarb / Ca++
- metabolic alkalosis
48
Example of a disease with increased 1-OH'ase activity
Sarcoidosis
49
> 60% of patients with primary hyperparathyrodism are...
post-menopausal women
50
Biochemical profile of primary hyperparathyrodism
- high PTH
- high Ca
- low P
- high / normal 1,25-(OH)2D3
51
Difference between PTH and PTHrP
PTH on chrom 11
| PTHrP on chrom 12
52
Similarities between PTH and PTHrP
first 8 AA on N term shows close homology
53
Where does PTHrP bind, and what effects does it have?
PTH receptor
| Mimic PTH effects
54
Is PTHrP common? Where can high concentrations of it usually be found?
Very common
| Breast milk
55
biochemical differences of PTH and PTHrP
PTH cause slight increase of 1,25-(OH)2D3
| PTHrP cause slight decrease of 1,25-(OH)2D3
56
PTHrP is produced in...
some tumours that cause humoral hypercalcemia of malignancy (HHM)
57
Common bone disorders
- osteomalacia & rickets
- paget's disease
- osteoporosis
58
is Ca++ a marker of bone disease?
Not necessarily; bone disease can occur even when Ca++ is normal
59
What is responsible for bone resorption? formation?
osteoclasts
| osteoblasts
60
Markers for bone resorption
deoxypyridinoline
61
deoxypyridinoline
collagen degradation product
62
markers for bone formation
- alkaline phosphatase
| - osteocalcin
63
alkaline phosphatase
bone specific isoenzyme
64
osteocalcin
produced by osteoblasts
65
Rickets
defects of bone & cartilage mineralization in children
66
What are the two bone diseases present in adults/children?
Osteomalacia
| Rickets
67
Osteomalacia
defective bone mineralization in adults
68
difference between Osteomalacia and Rickets
- adult vs. child
- cartilage also impacted in children
- same disease but different names for diff age
69
causes of rickets
vit D deficiency
70
Rickets is divided into...
- vit D dependent type I
| - vit D dependent type II
71
vit D dependent type I
- hereditory
- defective 1-OH'ase
- can't make 1,25(OH)2D3
72
Treatment for vit D dependent type I
give 1,25(OH)2D3
73
biochemical profile of vit D dependent type I
- high PTH
- low Ca++
- low 1,25(OH)2D
74
biochemical profile of vit D dependent type II
- high 1,25(OH)2D
75
vit D dependent type II rickets
vit D receptor defect
76
Paget's disease
- increased osteoclast activity
| - increased osteoblast activity, but new bone is not formed properly
77
clincal presentation of paget's diease
severe bone pain
| - loss of hearing (bones in ear)
78
biochemical profile of Paget's disease
- normal Ca
| - increased alkaline phosphatase activity
79
treatment of Paget's disease
- bisphosphate drug
| - calcitonin
80
relationship between calcitonin and osteoclasts
calcitonin can stop osteoclast activity
81
Who is more affected by osteoporosis? This is called...
post-menopausal women
| - primary osteoporosis
82
cause of primary osteoporosis?
unknown
83
cause of secondary osteoporosis?
Increased cortisol -> increased osteoclast activity
84
To maintain proper bone health, what 2 requirements must be met?
1. exercise
| 2. weight bearing (gravity, standing)
85
What are the 3 major forms of vit D supplements?
1. native vit D
2. 25(OH)D
3. 1,25(OH)2D
86
vit D deficiency caused by malnutrition / lack of sun / only breastfed baby should be treated by which form of vit D?
native
| Ca++ metabolites can be used if more severe
87
vit D deficiency caused by chronic liver disease should be treated by which form of vit D?
25(OH)D
1,25(OH)2D can also be used if severe
88
vit D deficiency caused by chronic renal disease should be treated by which form of vit D?
1,25(OH)2D
89
vit D deficiency caused by vit D dependent rickets type I should be treated by which form of vit D?
1,25(OH)2D
90
vit D deficiency caused by vit D dependent rickets type II should be treated by which form of vit D?
Nothing; insensitivity to vit D
