Calcium Dysregulation

Question 1

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

Answer 1

vitamin D

parathyroid hormone

Question 2

sources of vitamin D

Answer 2

synthesised in the skin

intake via diet

Question 3

parathyroid hormone is secreted from?

Answer 3

parathyroid gland

Question 4

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

Answer 4

kidney
bone
gut

Question 5

list a regulator of a decrease in serum calcium and phosphate

Answer 5

calcitonin

Question 6

calcitonin is secreted by?

Answer 6

thyroid parafollicular cells

Question 7

what is the active form of vitamin D?

Answer 7

calcitriol

Question 8

what is a good indicator of body vitamin D status?

Answer 8

serum 25-OH vitamin D

Question 9

how does calcitriol regulate its synthesis?

Answer 9

decreases transcription of 1 alpha hydroxylase

Question 10

outline vitamin D metabolism

Answer 10

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

Question 11

vitamin D from the diet is in what form?

Answer 11

vitamin D2

Question 12

effects of calcitriol

Answer 12

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

Question 13

actions of parathyroid hormone

Answer 13

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

Question 14

regulation of serum phosphate by FGF23

Answer 14

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

Question 15

what is Chvostek’s sign?

Answer 15

facial paresthesia

Question 16

what is Trousseau’s sign?

Answer 16

carpopedal spasm

Question 17

effect of hypocalcaemia

Answer 17

Sensitises excitable tissues; muscle cramps, tetany, tingling

Question 18

signs and symptoms of hypocalcaemia

Answer 18

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

Question 19

causes of hypocalcaemia can be split into?

Answer 19

low PTH levels

low vitamin D levels

Question 20

causes of hypocalcaemia due to low PTH?

Answer 20

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

Question 21

causes of hypocalcaemia due to low vitamin D?

Answer 21

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

Question 22

effect of hypercalcaemia

Answer 22

reduced neuronal excitability - atonal muscles

Question 23

signs and symptoms of hypercalcaemia

Answer 23

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

Question 24

causes of hypercalcaemia can be split into?

Answer 24

primary hyperparathyroidism malignancy

vitamin D excess

Question 25

primary hyperparathyroidism is usually due to?

Answer 25

parathyroid gland adenoma

Question 26

how does malignancy cause hypercalcaemia?

Answer 26

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

Question 27

increased PTH has what effect on serum calcium?

Answer 27

increases

Question 28

decreased PTH has what effect on serum calcium?

Answer 28

decreases

Question 29

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

Answer 29

due to autonomous PTH secretion from parathyroid adenoma

Question 30

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

Answer 30

high calcium low phosphate (increased renal excretion) high PTH

Question 31

treatment for primary hyperparathyroidism

Answer 31

parathyroidectomy

Question 32

untreated hyperparathyroidism has risks of?

Answer 32

``` osteoporosis renal calculi (stones) psychological impact of hypercalcaemia – mental function, mood ```

Question 33

what is secondary hyperparathyroidism?

Answer 33

normal physiological response to hypocalcaemia

Question 34

levels of Ca2+, PTH in secondary hyperparathyroidism?

Answer 34

low or low/normal calcium | PTH high secondary to low calcium

Question 35

causes of secondary hyperparathyroidism

Answer 35

vitamin D deficiency: diet, reduced sunlight | renal failure

Question 36

general treatment option for secondary hyperparathyroidism

Answer 36

vitamin D replacement

Question 37

treatment option for secondary hyperparathyroidism in those with normal renal function

Answer 37

give 25 hydroxy vitamin D > ergocalciferol (D2) | cholecalciferol (D3)

Question 38

treatment option for secondary hyperparathyroidism in those with renal failure

Answer 38

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

Question 39

when does tertiary hyperparathyroidism occur?

Answer 39

in chronic renal failure

Question 40

tertiary hyperparathyroidism

Answer 40

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

Question 41

treatment for tertiary hyperparathyroidism

Answer 41

parathyroidectomy

Question 42

what is the diagnostic approach to hypercalcaemia?

Answer 42

ALWAYS look at the PTH

Question 43

normal PTH response to hypercalcaemia is?

Answer 43

PTH falls

Question 44

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

Answer 44

high calcium | low/suppressed PTH

Question 45

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

Answer 45

hyperparathyroidism

Question 46

how to differentiate primary and tertiary hyperparathyroidism?

Answer 46

primary - renal fx normal | tertiary - renal fx > chronic failure

Question 47

diagnostic approach to vitamin D deficiency

Answer 47

Calcium will be low or low/normal | PTH will be high (hyperparathyroidism) secondary to the low calcium