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Endocrinology > Calcium Dysregulation > Flashcards

Calcium Dysregulation Flashcards

1
Q

list the main regulators of an increase in serum calcium and phosphate

A

vitamin D

parathyroid hormone

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2
Q

sources of vitamin D

A

synthesised in the skin

intake via diet

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3
Q

parathyroid hormone is secreted from?

A

parathyroid gland

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4
Q

vitamin D and PTH act where to decrease serum calcium and phosphate?

A

kidney
bone
gut

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5
Q

list a regulator of a decrease in serum calcium and phosphate

A

calcitonin

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6
Q

calcitonin is secreted by?

A

thyroid parafollicular cells

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7
Q

what is the active form of vitamin D?

A

calcitriol

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8
Q

what is a good indicator of body vitamin D status?

A

serum 25-OH vitamin D

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9
Q

how does calcitriol regulate its synthesis?

A

decreases transcription of 1 alpha hydroxylase

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10
Q

outline vitamin D metabolism

A

UVB > 7-dehydrocholesterol > pre-vitamin D3 > vitamin D3 > 25 hydroxylase > 25 (OH) cholecalciferol > 1 alpha hydroxylase > 1, 25 (OH)2 cholecalciferol

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11
Q

vitamin D from the diet is in what form?

A

vitamin D2

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12
Q

effects of calcitriol

A

bone: increased osteoblast activity
gut: ^ Ca2+/PO43- absorption
kidney: ^ Ca2+/PO43- reabsorption

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13
Q

actions of parathyroid hormone

A

bone: ^Ca2+ resorption
kidney: ^Ca2+ reabsorption, PO34- excretion, 1-alpha-hydroxylase
gut: indirectly via ^vitD synthesis > ^Ca2+/PO43- absorption

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14
Q

regulation of serum phosphate by FGF23

A

inhibits PO43- reabsorption in the kidneys by inhibiting Na+/PO43- transporters inhibits synthesis of calcitriol, causing less PO43- absorption from the gut

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15
Q

what is Chvostek’s sign?

A

facial paresthesia

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16
Q

what is Trousseau’s sign?

A

carpopedal spasm

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17
Q

effect of hypocalcaemia

A

Sensitises excitable tissues; muscle cramps, tetany, tingling

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18
Q

signs and symptoms of hypocalcaemia

A

Paraesthesia (hands, mouth, feet , lips)
Convulsions
Arrhythmias
Tetany

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19
Q

causes of hypocalcaemia can be split into?

A

low PTH levels

low vitamin D levels

20
Q

causes of hypocalcaemia due to low PTH?

A 
hypoparathyroidism
surgical - neck surgery
autoimmune
magnesium deficiency
congenital (agenesis, rare)
21
Q

causes of hypocalcaemia due to low vitamin D?

A

deficiency: diet, UV light, malabsorption, impaired production (renal failure)

22
Q

effect of hypercalcaemia

A

reduced neuronal excitability - atonal muscles

23
Q

signs and symptoms of hypercalcaemia

A

renal: nephrocalcnosis, kidney stones, renal colic
GI: anorexia, nausea, dyspepsia, constipation, pancreatitis
CNS: fatigue, depression, impaired concentration, altered mentation, coma

24
Q

causes of hypercalcaemia can be split into?

A

primary hyperparathyroidism malignancy

vitamin D excess

25
Q

primary hyperparathyroidism is usually due to?

A

parathyroid gland adenoma

26
Q

how does malignancy cause hypercalcaemia?

A 
Bony metastases produce local factors to activate osteoclasts
some cancers (eg squamous cell carcinomas) secrete PTH-related peptide that acts at PTH receptors
27
Q

increased PTH has what effect on serum calcium?

A

increases

28
Q

decreased PTH has what effect on serum calcium?

A

decreases

29
Q

why is there no negative feedback to PTH in parathyroid adenoma?

A

due to autonomous PTH secretion from parathyroid adenoma

30
Q

levels of Ca2+, PO43-, PTH in primary hyperparathyroidism?

A

high calcium
low phosphate (increased renal excretion)
high PTH

31
Q

treatment for primary hyperparathyroidism

A

parathyroidectomy

32
Q

untreated hyperparathyroidism has risks of?

A 
osteoporosis
renal calculi (stones)
psychological impact of hypercalcaemia – mental function, mood
33
Q

what is secondary hyperparathyroidism?

A

normal physiological response to hypocalcaemia

34
Q

levels of Ca2+, PTH in secondary hyperparathyroidism?

A

low or low/normal calcium

PTH high secondary to low calcium

35
Q

causes of secondary hyperparathyroidism

A

vitamin D deficiency: diet, reduced sunlight

renal failure

36
Q

general treatment option for secondary hyperparathyroidism

A

vitamin D replacement

37
Q

treatment option for secondary hyperparathyroidism in those with normal renal function

A

give 25 hydroxy vitamin D > ergocalciferol (D2)

cholecalciferol (D3)

38
Q

treatment option for secondary hyperparathyroidism in those with renal failure

A

can’t activate 25 hydroxy vitamin D preparations > Give Alfacalcidol - 1a hydroxycholecalciferol

39
Q

when does tertiary hyperparathyroidism occur?

A

in chronic renal failure

40
Q

tertiary hyperparathyroidism

A

Can’t make calcitriol
PTH increases (hyperparathyroidism)
Parathyroid glands enlarge (hyperplasia)
Autonomous PTH secretion causes hypercalcaemia

41
Q

treatment for tertiary hyperparathyroidism

A

parathyroidectomy

42
Q

what is the diagnostic approach to hypercalcaemia?

A

ALWAYS look at the PTH

43
Q

normal PTH response to hypercalcaemia is?

A

PTH falls

44
Q

levels of Ca2+/PTH in hypercalcaemia due to malignancy?

A

high calcium

low/suppressed PTH

45
Q

If patient with hypercalcaemia has raised PTH, the diagnosis is?

A

hyperparathyroidism

46
Q

how to differentiate primary and tertiary hyperparathyroidism?

A

primary - renal fx normal

tertiary - renal fx > chronic failure

47
Q

diagnostic approach to vitamin D deficiency

A

Calcium will be low or low/normal

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

Endocrinology (15 decks)

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