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rheumatoid arthritis, osteoarthritis, inflammatory arthritis, Lupus and scleroderma, others > CALCIUM AND BONE > Flashcards

CALCIUM AND BONE Flashcards

1
Q

Where is parathyroid hormone metabolised?

A

The kidney and liver

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2
Q

What is the half life of parathyroid hormone?

A

4 mins

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3
Q

What is the trigger for the release of parathyroid hormone?

A

A fall in plasma free ionised calcium

Rise in plasma phosphate (more chronic)

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4
Q

What are the key actions of parathyroid hormone? Name 4

A

Acts on kidney to promote calcium uptake
Promotes bone resorption by osteoclasts
Increases calcium uptake in the GI indirectly (by generating active vitamin D)
Promotes phosphate excretion in renal tubules

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5
Q

What type of hormone is vitamin D?

A

Steroid hormone

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6
Q

What are the forms of vitamin D measured in a blood test?

A

25-hydroxyvitamin D (2 and 3)

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7
Q

What are possible causes of vitamin D deficiency?

A

Lack of sunlight

Poor diet

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8
Q

Where is vitamin D activated? Name both organs

A

In the liver

In the kidney

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9
Q

What is the form of vitamin D metabolised in the kidney in step 2?

A

Calcitriol

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10
Q

What forms of vitamin D are normally given as supplements?

A

D2 and D3 (find names for these)

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11
Q

What percentage of the calcium in the circulation is ionised?

A

45%

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12
Q

What is the physiologically active form of calcium?

A

Ionised form

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13
Q

How are the other 55% (not ionised) of calcium circulating?

A

45% bound to albumin

10% complexed

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14
Q

What is the serum calcium result adjusted for?

A

Serum levels of albumin

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15
Q

What is the formula for working out the adjusted calcium result?

A

Adjusted calcium = total calcium + 0.02(40 - albumin)

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16
Q

What is the normal range for calcium?

A

2.2 - 2.6 mmol/L

17
Q

How can you distinguish between a parathyroid induced hypercalcaemia and hypercalcaemia caused by something else?

A

If hypercalcaemic plus suppressed PTH then this is due to something else. If hypercalcaemic plus raised PTH then this is probably due to parathyroid.

18
Q

What are PTH mediated causes of hypercalcaemia?

A

Calcium receptor defects

Primary or tertiary hyperparathyroidism

19
Q

What is the most common cause of hypercalcaemia?

A

Hypercalcaemia of malignancy

20
Q

What malignancies can cause hypercalcaemia?

A

Often bony metastases

21
Q

What does primary hyperparathyroidism mean?

A

Adenoma or hyperplasia of parathyroid

22
Q

What is secondary hyperparathyroidism?

A

Increased PTH due to lack of calcium. Could be as a result of renal failure or malabsorption.

23
Q

What is tertiary hyperparathyroidism?

A

This is due to a prolonged secondary hyperparathyroidism where the underlying cause of the initial calcium decrease is successfully treated.

24
Q

What are the most common causes of primary hyperparathyroidism?

A

Sporadic adenomas.

Also part of MEN type 1.

25
Q

What are the common symptoms of primary hyperparathyroidism?

A

Fatigue
Weakness
Kidney stones occur in 20% of cases
Psychiatric symptoms (eg depression)

26
Q

What is the treatment of primary hyperparathyroidism?

A

Surgical removal of the tumour.

27
Q

How can you know if the surgery has been a success before the operation is even finished?

A

Because the half life of PTH is so short that you can assess whether there has been a 50% drop in PTH levels.

28
Q

What are non-parathyroidal causes of hypocalcaemia?

A

Vitamin D deficiency

Renal failure

29
Q

What are parathyroid causes of hypocalcaemia?

A

Magnesium defiency

Hypoparathyroidism

30
Q

What markers can you look at to assess osteoblasts activity?

A

Alkaline phosphatase

Collagen peptides

31
Q

What markers can we look at to assess osteoporosis?

A

There are no good markers as the ones that we do use all suffer from high intraindividual variation.
We can look at urine NTX, plasma CTX, P1NP

32
Q

What are the systems involved in calcium homeostasis?

A

GI
Kidney
Skeleton
Parathyroid

rheumatoid arthritis, osteoarthritis, inflammatory arthritis, Lupus and scleroderma, others (38 decks)

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