Calcium metabolism 280721

Question 1

What are the consequences of hypercalcaemia

Answer 1

Stones, bones, groans, moans, nephrogenic DI

Question 2

What are the consequences of hypocalcaemia

Answer 2

CATS go numb

Question 3

What is the n ormal range for calciu,

Answer 3

2.2-2.6mmol/l

Question 4

How is the 1% calcium in serum divided

Answer 4

1) free ionised calcium - this is maintained at around 50%
2) 40% albumin bound
3) 10% citrate/phosphate bound

Question 5

What is the corrected calcium calculation

Answer 5

serum calcium + 0.02 x(40-serum albumin)

Question 6

what are the actions of PTH

Answer 6

activates 1 alpha hydroxylase which converts calcidiol to calcitriol
osteoclast activation -> calcium liberation
direct renal calcium resorption
direct renal phosphate excretion

Question 7

What is Vitamin D3 called and where is it from

Answer 7

animal product + sunlight = cholecalciferol

Question 8

D2

Answer 8

ergocalciferol, from plants

Question 9

How does cholecalciferol become calcitriol

Answer 9

Vitamin D3 / Cholecalciferol -> liver-> 25-hydroxy vitamin D3 -> under PTH -> kidneys-> 1, 25 dihydroxy vitamin D3 / Calcitriol

Question 10

summer hypercalcaemia

Answer 10

o Sarcoid = causes hypercalcemia (seasonal) – summer hypercalcemia
o In sunlight, calcium goes up (more vitamin D activation)

Question 11

• Role of 1,25 (OH)2 Vitamin D / Calcitriol:

Answer 11

o Intestinal Ca2+ absorption and intestinal phosphate absorption
o Critical for bone formation (with osteoblasts)
o Other physiological effects
 Vitamin D receptor controls many genes – cell proliferation, immune system
 Vitamin D deficiency associated with cancer, autoimmune disease, metabolic syndrome

Question 12

Osteomalacia clinical features

Answer 12

• Bone and muscle pain
• Increase fracture risk
• Bio-chem → low Ca2+ and phosphate and raised ALP
• Looser’s zones (pseudo fractures)

Question 13

Rickets clinical features

Answer 13

• Bowed legs Costochondral swelling

* Widened epiphyses at the wrists Myopathy (weak muscles)

Question 14

what are some of the causes of osteomalacia

Answer 14

o Bone is demineralised Caused by vitamin D deficiency
o Renal failure Anticonvulsants induce breakdown of Vitamin D (phenytoin)
o Lack of sunlight Chappatis – phytic acid (cause osteomalacia)

Question 15

what happens to the bone mass and bone structure and calcium in osteoporosis

Answer 15

o Loss of bone mass, but residual bone normal in structure
o Osteoporosis has bone loss but with a normal calcium
o Reduction in bone density with normal mineralisation
 Biochemistry NORMAL

Question 16

How is osteoporosis diagnosed

Answer 16

using DEXA scan (Dual energy X-ray absorptiometry):
 Hip (femoral neck) and lumbar spine
 T score – SD from mean of young healthy population – determine fracture (#) risk
 Z score – SD from mean of age-matched control – identify accelerated bone loss in younger people
 Osteoporosis – T score

Question 17

What are some of the treatments for osteoporosis

Answer 17

o Lifestyle
 Weight bearing exercise
 Stop smoking
 Reduce ETOH
o Drugs
 Vitamin D/Ca
 Bisphosphonates (alendronate) – decrease bone resorption – osteonecrosis of jaw
 Teriparatide – PTH derivative – anabolic
 Strontium – anabolic + anti-resorptive
 Oestrogens – HRT
 SERMs (oestrogen-like drug) – raloxifene (like Tamoxifen)
 Denosumab – biologic anti-RANK-L antibody

Question 18

what are the symptoms of hypercalcaemia

Answer 18

•	Symptoms
o	Polyuria or polydipsia 
o	Bones
o	Stones		
o	Abdo - constipation		
o	Neuro – confusion, seizures, coma 	
o	Unlikely unless Ca >3mmol/L (2.2-2.6)
o	Overlap with symptoms of hyperPTH

Question 19

what is the calcium, phosphate and PTH like in primary hyperparathyroidism

Answer 19

• Increased serum Ca
• Increased or inappropriately normal PTH
• Decreased serum phosphate
• Increased urine calcium due to hypercalcemia

Question 20

Familial hypocalciuric hypercalcaemia

Answer 20

o calcium sensing receptor CaSR mutation
o Reduced sensitivity to calcium
o Higher set point for PTH release

o Mild hypercalcaemia
o Reduced urine Ca

Question 21

What are the 3 types of hypercalcaemia in malignancy

Answer 21

1. Humoral hypercalcaemia of malignancy – squamous cell lung cancer
   a. PTHrP
2. Bone mets – breast ca
   a. Local bone osteolysis
3. Haematological malignancy – myeloma
   a. Cytokines

Question 22

Other types of nonPTH driven hypercalcaemia

Answer 22

• Sarcoidosis – non renal 1α hydroxylation
• Thyrotoxicosis – thyroxine leads to bone resorption
• Hypoadrenalism – renal Ca transport
• Thiazide diuretics – renal Ca transport
• Excess vitamin D – sunbeds

Question 23

Hypercalcaemia treatment

Answer 23

• FLUIDS (0.9% saline, 1L/hour and reassess)

• Treat underlying cause
• Cinacalcet acid – activates CaSR

Question 24

Pagets disease signs and symptoms

Answer 24

• Signs & symptoms:
o Bone pain Warmth Cardiac failure
o Deformity Fracture Malignancy
o Compression (blindness, deafness)

o Pelvis, femur, skull and tibia

Question 25

Investigations pagets and treatment

Answer 25

o Elevated alkaline phosphatase
 Ca and PO4 are NORMAL as…
 Osteoclasts and blasts are both active together
o Nuclear med scan / XR

• Treatment  Bisphosphonates for pain

Question 26

Hypocalcaemia signs and symptoms

Answer 26

• Signs and symptoms:
o Neuromuscular excitability  Chvostek’s sign (face), Trousseau’s sign, hyperreflexia
o Convulsions
• When diagnosing…
o 1st  repeat bloods and adjust for albumin (as the albumin can bind ionised calcium)
o 2nd  what is the PTH?

Question 27

what should you always do when checking blood calcium

Answer 27

repeat resuults and check albumin

Question 28

examples of secondary hyperparathyroidism

Answer 28

vit D deficiency, chronic kidney disease PTH resistence (pseudohypoparathyroidism)

Question 29

Pagets blood values

Answer 29

raised alk phos only

Question 30

vitamin D deficiency blood values

Answer 30

low cal low phos, high PTH, high alk phos, low vit D

Question 31

Renal failure blood values

Answer 31

very very low vit D, high PTH, low calcium, high phosphate, high PTH, high alk phos