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calcium dysregulation Flashcards

1
Q

which two factors increase serum calcium?

A

vitamin D parathyroid hormone

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2
Q

what decreases serum calcium?

A

calcitonin

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3
Q

where is calcitonin released from?

A

thyroid parafollicular cells

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4
Q

what happens to calcium levels if thyroidectomy is performed?

A

no effect

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5
Q

how does calcitonin reduce calcium?

A

acutely

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6
Q

pre-vitamin D3 is synthesised from which molecule?

A

7-dehydrocholesterol

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7
Q

vitamin D3 is synthesized from which molecule?

A

pre-vitamin D3

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8
Q

what catalyses the production of vitamin D3 in the skin?

A

UVB light

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9
Q

once vitamin D3 is in the blood circulation, where does it go and what is it converted into? which enzyme converts it?

A

liver 25(OH)cholecalciferol 25-hydroxylase

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10
Q

where is 25(OH)cholecalciferol hydroxylated, by which enzyme, and what does it become?

A
  • kidney
  • 1-alpha-hydroxylase
  • 1,25(OH)2 cholecalciferol
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11
Q

What is another name for 1,25(OH)2 cholecalciferol?

A

calcitriol

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12
Q

calcitriol is known as what type of vitamin D?

A

active vitamin D

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13
Q

What are the effects of calcitriol on the bone, gut, and kidney?

A
  1. Increased osteoblast activity
  2. Increased calcium and phosphate absorption in the gut
  3. Increased calcium and phosphate reabsorption in the kidney
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14
Q

What are the effects of PTH on the bone, gut and kidney, and what does this do to serum calcium and calcitriol synthesis?

A
  1. Increases osteoclast activity, stimulating calcium resorption from bone
  2. Increases calcium and phosphate reabsorption in the gut
  3. Increases calcium reabsorption in the kidney and phosphate EXCRETION. Also increases 1-alpha-hydroxylase activity in the kidney.

Overall increases serum calcium and calcitriol synthesis

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15
Q

How is phosphate excreted in kidneys?

A

Via sodium/phsophate cotransporter

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16
Q

What is the name of the factor secreted by bone which inhibits sodium/phosphate cotransporters and calcitriol in the kidney to prevent phosphate reabsorption/maximise excretion?

A

FGF23

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17
Q

How does PTH increase phosphate excretion in the kidneys?

A

PTH inhibits sodium/phosphate transporter, preventing from being reabsorbed and causing it to be excreted in the urine

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18
Q
  • paraesthesia
  • convulsions
  • arrhythmias
  • tetany

are symptoms of?

A

hypocalcaemia

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19
Q

CATS go numb - stands for? What does it mean in terms of a diagnosis?

A
  • convulsions
  • arrhythmias
  • tetany
  • numbness - paraesthesia

means you probably have hypocalcaemia

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20
Q

How do you test for Chvostek’s sign, what would you see?

A

Tap facial nerve on zygomatic arch, resulting in a twitch

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21
Q

Chvostek’s sign is a sign of?

A

hypocalcaemia

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22
Q

Trousseau’s sign is a sign of?

A

hypocalcaemia

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23
Q

How do you test Trousseau’s sign?

A

Pump up BP cuff - hand contracts and patient can’t relax it properly

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24
Q

what is a carpopedal spasm?

A

hand contracts and patient can’t relax it properly

25
name two causes of hypocalcaemia
1. hypoparathyroidism 2. low vitamin D levels
26
state 4 causes of hypoparathyroidism
1. neck surgery 2. autoimmune 3. magnesium deficiency 4. congenital ie. born without parathyroid glands
27
why can magnesium deficiency result in low PTH levels?
Magnesium is needed to release PTH
28
What are 4 causes of vitamin D deficiency?
1. poor diet 2. Lack of UV light 3. malabsorption 4. impaired production due to renal failure
29
what is the mnemonic for hypercalcaemia signs and symptoms?
stones, abdominal moans and psychic groans
30
What are the GI effects (abdominal moans) of hypercalcaemia?
anorexia, nausea, dyspepsia, constipation, pancreatitis
31
What are the CNS effects of hypercalcemia (psychic groans)?
* fatigue * depression * impaired concentration * altered mentation * coma
32
What level of calcium needs to be reached before going into a coma with hypercalcaemia?
\>3mmol/L
33
what is the name for the renal effects of hypercalcemia?
nephrocalcinosis (renal stones) and renal colic
34
Name 3 causes of hypercalcaemia?
1. Primary hyperparathyroidism 2. Malignancy in the bone or a PTH-related peptide released by an ectopic cancer 3. vitamin D excess (rare)
35
how do bony metastases cause hypercalcaemia?
produce local factors which activate osteoclasts
36
what is a cause of primary hyperparathyroidism??
parathyroid gland adenoma
37
primary hyperparathyroidism would result in what levels of these factors? 1. calcium 2. PTH 3. phosphate
High PTH and high calcium, low phosphate
38
In a healthy person, what happens when calcium falls?
calcium sensing receptor on PTH glands senses low calcium and stimulates PTH production to increase serum calcium
39
In someone with primary hyperparathyroidism, what happens to calcium and PTH?
* Parathyroid adenoma produces too much PTH * calcium increases but has no negative feedback to PTH due to autonomous PTH secretion from parathyroid gland
40
what is the treatment for hyperparathyroidism?
parathyroidectomy or vitamin D if secondary
41
what three things can untreated primary hyperparathyroidism lead to?
osteoporosis renal calculi low mood/poor mental function
42
What causes secondary hyperparathyroidism?
low calcium due to vitamin D deficiency OR renal failure
43
what happens during secondary hyperparathyroidism to PTH and calcium?
Calcium is low, so PTH increases to compensate
44
how do we treat a patient with normal renal function with secondary hyperparathyroidism compared to someone with renal failure?
Give 25 hydroxy vitamin D as they can convert this to cholecalciferol in the kidney in renal failure you need to give alfacalcidol - synthetic ACTIVE vitamin D
45
What causes tertiary hyperparathyroidism? How?
chronic renal failure leading to chronic vitamin D deficiency, decreasing calcium levels and driving PTH to increase and soon PT glands become autonomous
46
What happens to calcium levels in tertiary hyperparathyroidism?
they increase slowly over time
47
what is the treatment for tertiary hyperparathyroidism?
parathyroidectomy
48
what happens to the size of the parathyroid glands in tertiary hyperparathyroidism?
they enlarge (hyperplasia)
49
What is the first thing to look at in someone with hypercalcaemia?
Look at PTH
50
If PTH is low in hypercalcaemia what does that point to?
malignancy
51
If PTH is high in hypercalcaemia what does that point to?
hyperparathyroidism primary if renal function normal tertiary if chronic renal failure
52
If there is low calcium but high PTH, what does that point to?
secondary hyperparathyroidism
53
When measuring vitamin D, which form do we measure?
25(OH) cholecalciferol
54
55 year old South Asian gentleman presented to his GP with aches and pains. On examination he had evidence of proximal myopathy. His GP performed some blood tests: Normal renal function Serum calcium 2.10 (reference range 2.15 – 2.60 mmol/L) Serum phosphate 0.8 (reference range: 0.80 – 1.40 mmol/L) 25 hydroxyvitamin D 10 (reference range : 70 – 150 nmol/L) PTH 20 (reference range: 1.1 – 6.8 pmol/L). what's the diagnosis?
secondary hyperparathyroidism
55
Case 2 A 55 year old South Asian gentleman presented to his GP with loin pain, which was worse on passing urine. His GP detected microscopic haematuria on a urine dipstick. His GP checked some blood tests: Normal renal function Serum calcium 2.90 (reference range: 2.15 – 2.60 mmol/L ) Serum phosphate 0.6 (reference range: 0.80 – 1.40 mmol/L) 25 hydroxyvitamin D 84 (reference range: 70 – 150 nmol/L) PTH 12 (reference range: 1.1 – 6.8 pmol/L). what's the diagnosis?
primary hyperparathyroidism hypercalcaemia nephrocalcinosis (renal stones)
56
how should someone with primary hyperparathyroidism be treated?
Confirm diagnosis through ultrasound or nuclear medicine scan using a tracer which is taken up by parathyroid glands parathyroidectomy drink a lot of fluid to flush out the renal stones treatment for renal stones - shockwave therapy
57
A 51-year-old woman attends her GP’s surgery. She is tired, with aches and pains all over her body for several months. She feels low in mood. She has noticed that she has become more constipated previously. She had a left mastectomy and adjuvant radiotherapy for breast cancer 3 years ago. Her GP checks some blood tests: Normal renal function Serum calcium 3.00 (reference range: 2.15 – 2.60 mmol/L ) Serum phosphate 1.00 (reference range: 0.80 – 1.40 mmol/L) 25 hydroxyvitamin D 70 (reference range: 70 – 150 nmol/L) PTH \<1.1 (reference range: 1.1 – 6.8 pmol/L). what is the diagnosis?
hypercalcaemia caused by malignancy stimulating osteoclasts and born resorption
58
what's the treatment for bony metastases?
Give lots of fluids to flush kidneys to excrete as much calcium as possible - IV fluids bisphosphonate - switches off osteoclasts and stops them releasing calcium into circulation, helps with bone pain
59
what are the causes of hypoparathyroidism?
* surgical - neck surgery * auto-immune * magnesium deficiency * congenital

Endocrinology 2 (17 decks)

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