Calcium Homeostasis & Disorders

Question 1

how is calcium homeostasis achieved & maintained?

Answer 1

diet
gut absorption
PTH
Vit. D

Question 2

what affects gut absorption of calcium?

Answer 2

age
hormones
bowel pathology

Question 3

what affects PTH levels?

Answer 3

hyper/hypoparthryroidism

malignant hypercalcaemia

Question 4

what affects vit. D levels?

Answer 4

diet 
absorption 
renal 
liver 
UVB exposure 
drugs

Question 5

what kind of feedback controls calcium?

Answer 5

negative

Question 6

what kind of receptors are present on the parathyroid gland for calcium?

Answer 6

G-protein coupled recepetor

Question 7

what happens to PTH levels when calcium’s GPCR is activated?

Answer 7

PTH is suppressed

Question 8

what does Vit. D do?

Answer 8

encourages calcium deposition in bones & suppresses PTH

Question 9

what does PTH do?

Answer 9

increases calcium uptake, makes you store calcium in bones & prevents loss through kidneys

Question 10

what are the acute symptoms of hypercalcaemia?

Answer 10

thirst, dehydration, confusion, polyuria

Question 11

what are the chronic symptoms of hypercalcaemia?

Answer 11

myopathy, osteopaenia, fractures, depression, hypertension,

abdominal pain- pancreatitis, ulcers, renal stones

Question 12

what are the 2 main causes of hypercalcaemia?

Answer 12

primary hyperparathyroidism

malignancy

Question 13

what are some other causes of hypercalcaemia?

Answer 13

drugs
granulomatous disease
familial hypocalciuric hypercalcaemia
tertiary hyperparathyroidism

Question 14

what drugs can cause hypercalcaemia?

Answer 14

vit D

thiazides

Question 15

what biochemical picture do you need to diagnose hyperparathyroidism?

Answer 15

raised serum caclium
raised serum PTH
increased urine calcium excretion

Question 16

what are the malignant mechanisms that can cause hypercalcaemia?

Answer 16

• metastatic bone destruction
• PTHrp from solid tumours
• osteoclast activating factors

Question 17

what is hypocalciuric hypercalcaemia?

Answer 17

autosomal dominant station that deactivates the calcium sensing receptor

Question 18

how is hypocalciuric hypercalcaemia diagnosed?

Answer 18

Mild Hypercalaemia
Reduced urine calcium excretion
PTH may be (marginally) elevated
Genetic Screening

Question 19

what is osteoporosis?

Answer 19

Progressive systemic skeletal disease characterised by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture

Question 20

what are the common fracture sites in osteoporosis?

Answer 20

neck of femur
vertebral body
distal radius
humeral neck

Question 21

what predicts fracture risk independently of other risk factors?

Answer 21

bone mineral density

Question 22

osteopenia

Answer 22

low bone mass

Question 23

name some endocrine secondary causes of osteoporosis

Answer 23

hyperthyroidism
hyperparathyroidism
Cushing’s disease

Question 24

name some gastrointestinal secondary causes of osteoporosis

Answer 24

coeliac disease
IBD
chronic liver disease
chronic pancreatitis

Question 25

name some respiratory secondary causes of osteoporosis

Answer 25

CF | COPD

Question 26

what are bisphosphonates?

Answer 26

anti-resorptive agents

Question 27

what do bisphophonates do?

Answer 27

prevent bone loss at all sites vulnerable to osteoporosis

Question 28

what are the long term concerns of bisphosphonate therapy?

Answer 28

osteonecrosis of the jaw oesophageal Ca atypical fractures

Question 29

what is denosumab?

Answer 29

fully human monoclonal antibody that targets and binds with high affinity and specificity to RANKL

Question 30

RANKL

Answer 30

receptor activator of nuclear factor-kB ligand

Question 31

what are the adverse effects of denosumab?

Answer 31

hypocalcaemia eczema cellulitis

Question 32

what are the direct effects of corticosteroids on bone?

Answer 32

reduction of osteoblast activity & lifespan suppression of replication of osteoblast precursors reduction in calcium absorption

Question 33

wha are the indirect effects of corticosteroids on bone?

Answer 33

inhibition of gonadal & adrenal steroid production

Question 34

what is page's disease?

Answer 34

abnormal osteoclastic activity followed by increased osteoblastic activity

Question 35

what occurs in page's disease?

Answer 35

abnormal bone structure with reduced strength & increased fracture risk

Question 36

what is osteogenesis imperfecta?

Answer 36

rare group of genetic disorders mainly affecting bone

Question 37

what are the 3 main causes of hypocalcaemia?

Answer 37

hypoparathyroidism Vit. D deficiency chronic renal failure

Question 38

what is the emergency treatment of acute hypocalcaemia?

Answer 38

IV calcium gluconate 10 ml, 10% over 10 mins (in 50ml saline or dextrose)

Question 39

name some causes of hypoparathyroidism

Answer 39

``` Congenital absence (DiGeorge syndrome) Destruction (surgery, radiotherapy, malign) Autoimmune - most common Hypomagnesaemia Idiopathic ```

Question 40

why is magnesium important in calcium homeostasis?

Answer 40

calcium release from cells is dependent on magnesium

Question 41

what happens in magnesium deficiency

Answer 41

intracellular calcium is high & PTH release is inhibited

Question 42

what is pseudohypoparathyoridism?

Answer 42

genetic defect causing PTH resistance & resulting in low calcium but high PTH

Question 43

which gene is affected in pseudohypoparathyroidism?

Answer 43

GNAS 1

Question 44

what clinical signs occur in pseudohypoparathyroidism?

Answer 44

``` bone abnormalities obesity subcutaneous calcification learning disability brachdactyly ```

Question 45

brachdactyly

Answer 45

shortening of 4th metacarpal

Question 46

what is pseudo-pseudohypoparathyroidism?

Answer 46

same as psuedohypoparathyroidism with normal calcium levels