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Term 2 Med School > Regulation of calcium and phosphate > Flashcards

Regulation of calcium and phosphate Flashcards

1
Q

Recommended Calcium intake per day adults

A

1000mg

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2
Q

Calcium proportions in the body

A

99% skeleton and teeth - hydroxyapatite crystals
1% intracellular
0.1% extracellular

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3
Q

Plasma Calcium concentration

A

-2.5mmol/L
Active
Bound to plasma proteins or anions

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4
Q

Importance of calcium in the body: Functions

A 
neuromuscular excitability
bone strength 
factor 4 blood coagulation 
intracellular 2nd messenger
intracellular co-enzyme 
hormone / neurotransmitter coupling secretion
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5
Q

Importance of phosphate in the body: Functions

A

ATP
2nd messengers
DNA
extracellular phosphate is inversely proportional to calcium conc, controlled by same hormones

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6
Q

Increase calcium levels in blood

A

Parathyroid hormone - parathyroid glands
Vitamin D - synthesized in skin or diet
act on kidneys bone and gut

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7
Q

Decrease calcium levels in blood

A

Calcitonin - thyroid parafollicular cells.

No negative effects if cells are removed eg thyroidectomy.

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8
Q

Vitamin D2 is from

A

diet - ergocalciferol

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9
Q

Vitamin D3 is from

A

sunlight - cholecalciferol

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10
Q

Production of Calcitriol

A

25 hydroxylase in liver

1 alpha - hydroxylase in kidney.

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11
Q

Measure Vitamin D status

A

measure serum 25-OH vitamin D.

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12
Q

Regulation of Calcitriol synthesis

A

Negative feedback

Calcitriol decreases transcription of 1 alpha-hydroxylase enzyme

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13
Q

Effects of Calcitriol

A

Increase serum Ca
Kidney - increased reabsorption of Ca2+ and PO43-
Small intestine increased Ca2+ and PO43- reabsorption
Stimulates osteoblasts

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14
Q

Parathyroid hormone secretion location and method

A

Chief cells in parathyroid glands as large precursor

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15
Q

Parathyroid hormone regulation

A

PTH secretion inversely proportional to serum calcium.
G - protein coupled calcium sensing receptor detects serum calcium
High - less PTH
Low - more PTH
Chief cells also have calcitriol receptors - negative feedback

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16
Q

Effects of Parathyroid hormone

A

Increase blood Ca
Kidney - increases Ca reabsoption
Decreases PO reabsorption
Increases 1 alpha-hydroxylase activity - leading to more Vit D synthesis
Increases bone resorption, consuming Ca from bone (osteoclasts)

17
Q

Parathyroid hormone in bone

A

OsteoBlast - build bone, PTH receptor converts to OsteoClast - consume bone to increase serum Ca

18
Q

Calcitonin secretion and function

A

Parafollicular cells of thyroid gland - detect high Ca
Reduces serum calcium
thyroidectomy does not affect serum calcium

19
Q

Calcitonin effects

A

Reduce plasma Ca
Kidney - increase Ca excretion
Decrease osteoclast activity

20
Q

FGF23 function

A

Inhibits Na/PO co transporter in kidney, decreases reabsorption of PO and inhibits calcitriol -
Leading to less PO reabsorption from gut

21
Q

High serum calcium

A

Hypercalcaemia

22
Q

Low serum calcium

A

Hypocalcaemia

23
Q

Hypercalcaemia effects

A

Ca blocks Na influx, so less membrane excitability - atonal muscles.

24
Q

Hypocalcaemia effects

A

Greater Na influx, so more membrane excitability - neuromuscular irritability

25
Q

Hypocalcaemia symptoms

A 
CATs go numb
sensitises excitable tissues - muscle cramps, paraesthesia 
convulsions
arrhythmias
Tetany (tetanic seizure)
26
Q

Signs of hypocalcaemia

A

Chvostek’s sign - twitching of facial muscles after tap.
Trousseau’s sign - inflation of BP cuff, carpopedal spasm.
Neuromuscular irritability due to hypocalcaemia

27
Q

Causes of hypocalcaemia

A 
Low PTH levels - hypoparathyroidsim
   Surgical
   Auto-immune
   Magnesium deficiency
   Congenital
Vitamin D deficiency
28
Q

Causes of Vitamin D deficiency

A 
Dietary insufficiency
Inadequate sun exposure
Liver disease - 25 hydroxylase
Renal disease - 1 alpha-hydroxylase
RARE - Vit D receptor defects
29
Q

Consequence of vitamin D deficiency

A

Lack of bone mineralisation - soft bones
Children - rickets
Adults - osteomalacia - fractures, proximal myopathy

30
Q

Signs of hypercalcaemia

A

Stones, abdominal moans and psychic groans.
Stones - nephrocalcinosis - kidney stones
Abdominal moans - GI effects, anorexia, nausea, constipation
Psychic groans - CNS effect, fatigue, depression, coma

31
Q

Causes of hypercalcaemia

A 
Primary hyperparathyroidism 
- too much PTH 
- parathyroid gland adenoma
- no neg feedback, high PTH and high calcium
Cancer : 
- bone metastases - activate osteoclasts
- squamous cell carcinomas - PTH related peptide mimics PTH
RARE - vit d excess
32
Q

Phosphate reabsorbed in the kidney by

A

sodium phosphate co-transporter

Term 2 Med School (11 decks)

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