Disorders of calcium metabolism Flashcards

1
Q

Normal serum calcium range?

A

2.2-2.6

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2
Q

Calcium metabolism controled by?

A

PTH, 1,25(OH)2D and calcitonin

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3
Q

Average dietry intake?

A

25mmol per day, 10mmol absorbed.

Avrage loss 10mmol via gut and kidney

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4
Q

Calcium protein binidng is dependent on?

A

pH, and is decreasd by acidosiss, and increaed by alkalosiss.

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5
Q

what does PTH cause?

A

increase rna tubular reabsorption and calcium from bone

Decreases reabsorption of phosphate

Stimulates 1alpha hydroxylase in kidney

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6
Q

Exaplin vitamin D metaolism?

A

Vitamin D
•Diet, Endogenous (sunlight)
•Vitamin D => liver => 25 (OH) D
•25 (OH) D => kidney => 1,25 (OH) D
•Increased by Circulating D and PTH
•Causes absorption of Calcium, phosphate in gut.

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7
Q

Where is calcitonini ecreted from and what dioes it do?

A

Parafollicular C cells of the thyroid
•Secretion stimulated by calcium, gastrin, glucagon and whiskey.
•Causes small fall in serum calcium

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8
Q

Causes of hypocalcaemia?

A

Hypoparathyroidism
•Pseudohypoparathyroidism
•Vit D deficiency
•Magnesium deficiency
•B12 deficiency
•Malabsorption

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9
Q

Investigation for hypocalcaemia?

A

Bone profile: Ca2+, PO4- , albumin, bicarbonate, alkaline phosphatase
•Serum magnesium
•FBC + ESR
•liver profile
•Renal profile
•PTH + 25(OH) D
•B12

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10
Q

Featurs of hypocalcaemia?

A

Usually symptomatic if calcium < 2.0mmol/L
Nervous system
•Paraesthesiae
•Tetany
•Seizures and psychosis
Ocular
•Cataracts
Cardiac
•Arrhythmias, heart block

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11
Q

how to treat hypocalcaemia?

A

Tetany or seizures
•10 ml IV calcium gluconate 10% + repeat as required
•Start calcitriol
•Oral Calcium supplements
•Oral Magnesium supplements

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12
Q

treat hypoparathyroidism?

A

Autoimmune or post thyroid surgery
•Present with symptoms of hypocalcaemia
•PTH low or un-recordable
•Serum PO4- high but creatinine normal
•Treat with calcitriol and thiazides
–Thiazides reduce renal leak of Ca2+

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13
Q

what is pseudohypoparathyroidism?

A

Rare inherited disease
•Defect of PTH receptor with PTH resistance
•High PTH but low Ca2+ and high PO4-
•Associated skeletal abnormalities
–eg short stature and shortened metacarpals
•May have low IQ and other hormone resistance
–eg thyroid and gonadal
•Treat with calcitriol

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14
Q

what is osteomacia?

A

Severe prolonged Vit D deficiency causes osteomalacia (rickets in children)

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15
Q

pathology of osteomlacia?

A

Severe prolonged Vit D deficiency causes osteomalacia (rickets in children)

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16
Q

featurs of steomaacia?

A

Proximal myopathy • Bone pains • Pseudofractures on Xray – Pubic rami, ribs, femoral neck • osteoporosis
• High alkaline phosphatase • low Ca2+, low PO4- • PTH high, 25[OH]D low

17
Q

who definition of osteoprosis?

A

WHO definition of osteoporosis is a bone mineral density (BMD) of 2.5 standard deviations or more below the mean value for young normal adults (a T-score of –2.5)

18
Q

secndary causes of oteoporosis?

A

Endocrine • thyrotoxicosis • hypogonadism • hyperparathyroidism • Cushing’s disease
Gastrointestinal • malabsorption
Drugs • steroids • alcoholism
Malignancy • myeloma
Rheumatoid arthritis

19
Q

selective ostogen rceptor moduators?

A

Raloxifene, Tamoxifen • No stimulation of endometrium • Increases risk of DVT, PE and hot flushes • Not as potent as bisphosphonates • Reduces risk of vertebral fractures only • Small rises in bone density

20
Q

list of oral bisphosphonates!

A

Alendronte, Ibandronate definitely prevent all types of osteoporotic fracture eg hip, spine and wrist •Risedronate less potent than alendronate and data from studies less consistent •Increase bone density at all relevant sites •Once weekly dosage and now once monthly dosage

21
Q

iv bisphosphonates?

A

Ibandronate 3mg every 3 months •Zoledronate 5mg annually •Clodronate 1500mg every 3 months

22
Q

teriparatide?

A

stimulates bone formationStimulates bone formation •90% reduction in vertebral fracture risk •50% reduction in non-vertebral fractures •Daily injection •Costs £300 per month •Second line treatment

23
Q

strontium ranelate?

A

Dual action inhibits osteoclast and stimulates bone formation •Reduces risk of both vertebral and non vertebral fractures •Simple oral administration •No upper GI side effects •Does cause diarrhoea

24
Q

other therapies?

A

Intra-nasal calcitonin used for treating vertebral fracture pain •Cyclical etidronate •HRT •Vertebroplasty •Physical activity

25
Q

pagets?

A

Focal abnormality of bone remodelling •excess and disorganised bone turnover –woven bone •sclerosis and lysis •affects 4% of the elderly •affects 1 or more bones

26
Q

how to diagnose pagets?

A

Serum ALP •fasting urine hydroxyproline/creatinine •Xrays •isotope bone scan

27
Q

bone structure?

A

Composite material with organic and inorganic phase •70% is mineral •30% extracellular matrix •bone is cellular and vascular •bone is constantly resorbed and reformed - bone turnover •normal bone is v strong and not brittle

28
Q
A