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Year 3 Endo > Calcium Dysregulation > Flashcards

Calcium Dysregulation Flashcards

1
Q

What can increase Calcium in the body?

A

Vitamin D

Parathyroid hormone

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2
Q

What can decrease Calcium in the body?

A

Calcitonin

Not sure of physiological role

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3
Q

What is Calcitonin secreted by?

A

Thyroid parafollicular cells

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4
Q

What are the main steps of Vitamin D metabolism

A

UVB shines on the skin
Converts 7-dehydrocholesterol to Pre-Vitamin D3
Converts to Vitamin D3

In the liver 25-hydroxylase converts it to 25(OH)cholecalciferol

In the Kidney 1-alpha-hydroxylase converts to 1,25(OH)2 cholecalciferol

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5
Q

What is the active form of Vitamin D?

A

1,25(OH)2 cholecalciferol

aka Calcitriol

Cannot be measured

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6
Q

What do you measure?

A

Good marker for how much Vitamin D someone has

25(OH)cholecalciferol

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7
Q

What does effect does Calcitriol have on 1-alpha hydroxylase?

A

Negative feedback

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8
Q

What are the effects of Calcitriol?

A

Absorb phosphates and calcium in the gut

Increased osteoblast activity

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9
Q

What are the effects of PTH?

A

Increased calcium and phosphate reabsorption in the gut by increasing the synthesis of Calcitriol
(Increases 1-alpha hydroxylase activity)

Increases reabsorption of calcium and excretion of phosphate in kidney

PTH stimulates osteoclasts to reabsorb calcium from bone

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10
Q

What is the net effect of PTH?

A

Increases synthesis of Calcitriol

Increase Ca mobilisation from bone

Increases plasma Calcium

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11
Q

What are the signs of Hypocalcaemia?

A

Paraesthesia
Convulsions
Arrhythmias
Tetany

CATS go numb

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12
Q

What are the two signs that are present with hypocalcaemia?

A

Chvosteks’ sign

Trousseau’s sign

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13
Q

What causes low PTH levels?

A

Surgical - neck surgery
Auto-immune
Magnesium deficiency
Congenital (agenesis, rare)

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14
Q

What causes low Vitamin D?

A

Deficiency - diet, UV light, malabsorption, impaired production (renal failure)

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15
Q

What are the signs of hypercalcaemia?

A

Stones
Abdominal moans
Psychic groans

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16
Q

What are stones?

A

Renal effects

Nephrocalcinosis- kidney stones, renal colic

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17
Q

What are abdominal moans?

A 
Anorexia
Nausea
Dyspepsia
Constipation
Pancreatitis
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18
Q

What are psychic groans?

A

CNS effects

Fatigue, depression, impaired concentration, altered mentation, coma (usually >3mmol/L)

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19
Q

What is the case of hyper calcaemia?

A

Primary hyperparathyroidism

Malignancy

Vitamin D excess (rare)

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20
Q

What are the features of primary hyperparathyroidism?

A

Too much PTH
Usually due to a parathyroid gland adenoma
No negative feedback - high PTH, but high calcium

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21
Q

What are the features of malignancy causing hypercalcaemia?

A 
Bony metastases produce local factors to activate osteoclasts
Certain cancers (eg squamous cell carcinomas) secrete PTH-related peptide that acts at PTH receptors
22
Q

What happens when serum calcium falls?

A

Feedback to parathyroid gland

Calcium sensor receptor senses this and stimulates PTH production

23
Q

What happens when serum calcium is high?

A

Feedback to parathyroid gland

Calcium sensor receptor senses this and inhibits PTH production

24
Q

What is an adenoma?

A

benign tumour of a endocrine gland

25
Q

What would a parathyroid adenoma result in?

A

Over production of PTH
Increases serum calcium
Tumour does not respond to negative feedback

Primary hyperparathyroidism

26
Q

What is the biochemistry of hyperparathyroidism?

A

High calcium

Low phosphate - increased renal phosphate excretion (inhibition of Na/Phosphate transporter in kidney)

High PTH

27
Q

What is the treatment of primary hyperparathyroidism?

A

Parathyroidectomy is treatment of choice for primary hyperparathyroidism

28
Q

What are the risks of untreated hyperparathyroidism?

A 
Osteoporosis
Renal calculi (stones)
Psychological impact of hypercalcaemia – mental function, mood
29
Q

How does secondary hyperparathyroidism occur?

A

Calcium is low

Sensed and PTH is stimulated

30
Q

How are 1ry and 2ry hyperparathyroidism different?

A

In 1ry calcium is high

31
Q

What is the most common form of secondary hyperparathyroidism?

A

Vitamin D deficiency

32
Q

What causes Vitamin D deficiency?

A

Commonly- diet, reduced sunlight

Less common cause is renal failure (can’t make 1-alpha hydroxylase)

33
Q

How do you treat secondary hyperparathyroidism?

A

Vitamin D replacement

Give 25 hydroxy vitamin D

Patient converts this to 1,25 dihydroxy vitamin D via 1a hydroxylase

Ergocalciferol 25 hydroxy vitamin D2

Cholecalciferol 25 hydroxy vitamin D3

34
Q

How do you treat secondary hyperparathyroidism in those with renal failure?

A

inadequate 1a hydroxylation, so can’t activate 25 hydroxy vitamin D preparations
Give Alfacalcidol - 1a hydroxycholecalciferol

35
Q

What causes tertiary hyperparathyroidism?

A

Chronic kidney disease
Chronic Vitamin D deficiency
Chronic low calcium

Increase in PTH to try and restore Ca to normal

Parathyroid glad become autonomous and overactive

Eventual excess of calcium

36
Q

How do you treat tertiary hyperparathyroidism?

A

Parathyroidectomy

37
Q

Summarise primary hyperparathyroidism?

A

Parathyroid adenoma, makes too much PTH

Calcium increases, but PTH stays high (no negative feedback)

38
Q

Summarise secondary hyperparathyroidism?

A

Normal physiological response to low calcium (commonly caused by low vitamin D)
Calcium low/low-normal, PTH high

39
Q

Summarise tertiary hyperparathyroidism?

A

Complication of chronic renal failure and prolonged calcitriol deficiency
Initially calcium falls and PTH rises (secondary hyperparathyroidism), but over a long period high PTH drive by enlarged parathyroid glands increases calcium

40
Q

How do you diagnose hypercalcaemia?

A

Always look at the PTH

41
Q

How will hypercalcaemia caused by malignancy present?

A

Normal PTH response to hypercalcaemia is for PTH to fall
Hypercalcaemia due to malignancy
High calcium (hypercalcaemia)
Low/suppressed PTH

42
Q

If PTH is high how do decide which form of hyperparathyroidism it is?

A

Primary hyperparathyroidism if renal function is normal (eg parathyroid adenoma)

Tertiary hyperparathyroidism (all 4 glands enlarged – hyperplastic) if chronic renal failure

43
Q

How do you diagnose Vitamin D deficiency?

A

Calcium will be low or low/normal

PTH will be high (hyperparathyroidism) secondary to the low calcium

Vitamin D is measured as 25 (OH) vitamin D

Calcitriol (1,25 dihydroxy vitamin D) is very difficult to measure

44
Q

Define hypoparathyroidism?

A

deficiency of plasma parathyroid hormone (PTH) synthesis and secretion

wide variety of presentations e.g. asympto with low Ca or acutely unwell with NMJ related symptoms

45
Q

What are the causes of hypoparathyroidism?

A

Post-thyroid surgery (most commonly)
Autoimmune destruction
Destruction due to tumour

46
Q

What would bloods show in hypoparathyroidism?

A

Low albumin corrected total calcium
Low or inappropriately normal PTH
Maybe low Vit D
Maybe low Mg

47
Q

What are some presenting features of hypoparathyroidism?

A

CATS go numb
Chronic alcoholism
History of thyroid surgery
Poor memory and slow thinking

48
Q

What investigations are done for hypoparathyroidism?

A 
Serum calcium
Serum albumin (if low will give falsely low calcium)
ECG
PTH
Vit D
Mg
49
Q

What are signs of hypocalcaemia on ECG?

A

Prolonged QT interval

50
Q

What is the management of hypoparathyroidism?

A

If severe: IV calcium

Oral calcium + low dose calcitriol

51
Q

What is the management for hypercalcaemia of malignancy?

A

IV saline

IV bisphosphonate e.g. zolendronic acid

Year 3 Endo (5 decks)

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