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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
Q

How to remember symptoms of hypocalcaemia?

A

(CATs go numb)

26
Q

What is used as ASSESSMENT FOR HYPOCALCAEMIA:

A

Chvosteks sign

TROUSSEAU’S SIGN:

27
Q

What is Chvosteks sign

A

 Tap facial nerve just below zygomatic arch
 Positive response= twitching of facial muscles
 Indicates neuromuscular irritability due to hypocalcaemia

28
Q

What is TROUSSEAU’S sign

A

 Inflation of BP cuff for several minutes

 Positive response= carpopedal spasm= neuromuscular irritability due to hypocalcaemia

29
Q

CAUSES OF HYPOCALCAEMIA (4)

A
  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
Q

HYPERCALCAEMIA:

SIGNS AND SYMPTOMS: (3)

A

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
Q

Saying to remember hypercalcaemai symptoms?

A

‘stones, abdominal moans and psychic groans’

32
Q

Causes of hypercalcaemia

A
  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
Q

Hyperparathyroidism levels of:
Calcium
Phosphate
PTH

A

Calcium - raised
Phosphate - low
PTH - raised

34
Q

Hypercalcaemia of malignancy levels of:
Calcium
Phosphate
PTH

A

Calcium - Raised
Phosphate - normal or raised
PTH - Low

35
Q

VITAMIN D DEFICIENCY STATES results in: (4)

A

softening of bone, bone deformities, bone pain; severe proximal myopathy

36
Q

Result of vit D deficiency in children?

A

Rickets

37
Q

Result of vit D deficiency in adults?

A

OSTEOMALACIA

38
Q

what is primary hyperparathyroidism

A

No negative feedback of calcium on PTH secretion, autonomous PTH secretion despite hypercalcaemia

39
Q

What is secondary hyperparathyroidism often

A

Vit D deficiency usually, so poor calcium absorption so PTH increases

40
Q

Effects of VitD? (4)

A

Calcium absorption in gut
Calcium maintenance n bone
Calcium renal increased absorption
-ve feedback on PTH

41
Q

Why might Ca level be normal in vitamin D deficiency

A

may be normal if secondary hyperparathyroidism has developed

42
Q 
VIt D deficiency serum levels of:
VitD
Calcium
Phosphate
PTH
A

Vit D- low obvs
Calcium - low or normal if secondary hyperparathyroidism has developed
Phosphate - low
PTH - high

43
Q

TREATMENT OF VIT D DEFICIENCY:

IN PATIENTS WITH NORMAL RENAL FUNCTION?

A

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
Q

TREATMENT OF VIT D DEFICIENCY:

IN PATIENTS WITH RENAL FAILURE:

A

Inadequate 1alpha hydroxylation Can’t activate 25 hydroxyl vit D preparations

Give ALPHACALCIDOL 1alpha hydroxycholecalciferol

45
Q

Alphacalcidol is used in….

A

TREATMENT OF VIT D DEFICIENCY:

IN PATIENTS WITH RENAL FAILURE

46
Q

Vit D excess can lead to … (2)

A

hypercalcaemia and hypercalciuria due to increased intestinal absorption of calcium

47
Q

Vit D excess can occur as result of (2)

A
  • 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
Q

cholecalciferol is made by…

A

the skin and UV

49
Q

ergo is absorbed from …

A

diet

50
Q

Why is osteomalacia and rickets reemerging in the UK

A

Shit diet and not much sunlight bc of lifestyles now

Endocrinology Y2 (18 decks)

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