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Endocrinology Y2 > Calcium and Phosphate Regulation > Flashcards

Calcium and Phosphate Regulation Flashcards

1
Q

3 effects of PTH?

A
  • PTH increases kidney calcium reabsorption
  • PTH promotes calcium release from the bone
  • PTH regulates conversion of inactive vitD to active vitD (calcitriol) (which promotes calcium reabsorption from the gut
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2
Q

Effect of PTH on a PCT cell?

A

Inhibits sodium/phosphate cotransporters

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3
Q

PRIMARY HYPERPARATHYROIDISM causes increased X excretion

A

phosphate

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4
Q

What hormone Inhibits sodium/phosphate cotransporters (2)

A

PTH and FGF23

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5
Q

What does FGF23 do

A

inhibits reabsorption of phosphate by the cotransporter

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6
Q

What secretes FGF23

A

Osteocytes

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7
Q

Effects of FGF23? (2)

A

inhibits reabsorption of phosphate by the cotransporter

can also inhibit calcitriol

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8
Q

What inhibits PTH secretion

A

Calcium binding to Ca receptor in the parathyroid

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9
Q

Effect on PTH with increased Ca in serum?

A

MORE PTH INHIBITION

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10
Q

Vitamin D is only active after ….

A

it has been hydroxylated to CALCITRIOL

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11
Q

Active form of vit d?

A

calcitriol

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12
Q

Inactive form of vit D?

A

Cholecalciferol

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13
Q

Where is vit D converted to calcitriol

A

in the kidney

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14
Q

What enzyme converts 25OH-D3 to calcitriol

A

Renal 1 alpha hydroxylase

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15
Q

Source and name of VitD3?

A

from skin through UV light makes cholecalciferol

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16
Q

Source and name of VitD2?

A

From diet, ergocalciferol

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17
Q

What hormone stimulates renal 1alpha-hydroxylase conversion of 25OH-D3 to calcitriol

A

PTH

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18
Q

What are cholecalciferol and ergocalciferol converted to

A

25OH-D3

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19
Q

Where are cholecalciferol and ergocalciferol converted to 25OH-D3

A

Liver

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20
Q

Liver converts what to what (re. vit D)

A

Cholecalciferol and ergocalciferol converted to 25OH-D3

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21
Q

Causes of vit D deficiency?

A
  1. MALABSORPTION OR DIETARY INSUFFICIENCY
  2. LACK OF DIRECT
  3. LIVER DISEASE
  4. RENAL DISEASE
  5. RECEPTOR DEFECTS (vitamin D resistant rickets Rare)
    - autosomal recessive
    - resistant to vitamin D treatment
22
Q

HOW DO HIGH EC CALCIUM AFFECT NERVE AND SKELETAL MUSCLE EXCITABILITY?

A

Ca2+ blocks Na+ influx, so there’s less membrane excitability

23
Q

HOW DO LOW EC CALCIUM AFFECT NERVE AND SKELETAL MUSCLE EXCITABILITY?

A

enables greater Na+ influx, so more membrane excitability

24
Q

SIGNS AND SYMPTOMS OF HYPOCALCAEMIA

A

Parasthesia (tingling - hands, mouth, feet, lips)
Convulsions
Arrhythmias
Tetany

25
How to remember symptoms of hypocalcaemia?
(CATs go numb)
26
What is used as ASSESSMENT FOR HYPOCALCAEMIA:
Chvosteks sign | TROUSSEAU’S SIGN:
27
What is Chvosteks sign
 Tap facial nerve just below zygomatic arch  Positive response= twitching of facial muscles  Indicates neuromuscular irritability due to hypocalcaemia
28
What is TROUSSEAU’S sign
 Inflation of BP cuff for several minutes |  Positive response= carpopedal spasm= neuromuscular irritability due to hypocalcaemia
29
CAUSES OF HYPOCALCAEMIA (4)
1. Vitamin D deficiency 2. Low PTH levels Hypoparathyroidism - surgical neck surgery - Auto-immune - Magnesium deficiency 3. PTH resistance e.g. pseudohypoparathryoidism 4. Renal failure - Impaired 1alpha hydroxylation - Decreased production of 1,25(OH)2D3 (liver failure too probably0)
30
HYPERCALCAEMIA: | SIGNS AND SYMPTOMS: (3)
STONES- RENAL EFFECTS: - Polyuria and thirst - Nephrocalcinosis, renal colic, chronic renal failure] ABDOMINAL MOANS- GI EFFECTS: - Anorexia, nausea, dyspepsia, constipation, pancreatitis PSYCHIC GROANS- CNS EFFECTS: Fatigue, depression, impaired concentration, altered mentation, coma
31
Saying to remember hypercalcaemai symptoms?
'stones, abdominal moans and psychic groans’
32
Causes of hypercalcaemia
1. Primary hyperparathyroidism 2. Malignancy Tumours/metastases often secrete a PTH-like peptide 3. Conditions with high bone turnover (hyperthyroidism, Paget’s disease of bone- immobilised patient) 4. Vitamin D excess (rare)
33
Hyperparathyroidism levels of: Calcium Phosphate PTH
Calcium - raised Phosphate - low PTH - raised
34
Hypercalcaemia of malignancy levels of: Calcium Phosphate PTH
Calcium - Raised Phosphate - normal or raised PTH - Low
35
VITAMIN D DEFICIENCY STATES results in: (4)
softening of bone, bone deformities, bone pain; severe proximal myopathy
36
Result of vit D deficiency in children?
Rickets
37
Result of vit D deficiency in adults?
OSTEOMALACIA
38
what is primary hyperparathyroidism
No negative feedback of calcium on PTH secretion, autonomous PTH secretion despite hypercalcaemia
39
What is secondary hyperparathyroidism often
Vit D deficiency usually, so poor calcium absorption so PTH increases
40
Effects of VitD? (4)
Calcium absorption in gut Calcium maintenance n bone Calcium renal increased absorption -ve feedback on PTH
41
Why might Ca level be normal in vitamin D deficiency
may be normal if secondary hyperparathyroidism has developed
42
``` VIt D deficiency serum levels of: VitD Calcium Phosphate PTH ```
Vit D- low obvs Calcium - low or normal if secondary hyperparathyroidism has developed Phosphate - low PTH - high
43
TREATMENT OF VIT D DEFICIENCY: | IN PATIENTS WITH NORMAL RENAL FUNCTION?
Give 25 hydroxy vit D Patient converts this to 1,25 dihydroxy vit D via 1alpha hydroxylase (ERGOCALCIFEROL= 25 hydroxy D2 and CHOLECALIFEROL= 25 hydroxy D3)
44
TREATMENT OF VIT D DEFICIENCY: | IN PATIENTS WITH RENAL FAILURE:
Inadequate 1alpha hydroxylation Can’t activate 25 hydroxyl vit D preparations Give ALPHACALCIDOL 1alpha hydroxycholecalciferol
45
Alphacalcidol is used in....
TREATMENT OF VIT D DEFICIENCY: | IN PATIENTS WITH RENAL FAILURE
46
Vit D excess can lead to ... (2)
hypercalcaemia and hypercalciuria due to increased intestinal absorption of calcium
47
Vit D excess can occur as result of (2)
- Excess treatment with active metabolites of vit D (e.g. alphacalcidol) - Granulomatous diseases such as sarcoidosis, leprosy and TB (macrophages in the granuloma produce 1alpha hydroxylase to convert 25(OH) D to active metabolite
48
cholecalciferol is made by...
the skin and UV
49
ergo is absorbed from ...
diet
50
Why is osteomalacia and rickets reemerging in the UK
Shit diet and not much sunlight bc of lifestyles now

Endocrinology Y2 (18 decks)

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