Disorders of calcium metabolism

Question 1

Normal serum calcium range?

Answer 1

2.2-2.6

Question 2

Calcium metabolism controled by?

Answer 2

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

Question 3

Average dietry intake?

Answer 3

25mmol per day, 10mmol absorbed.

Avrage loss 10mmol via gut and kidney

Question 4

Calcium protein binidng is dependent on?

Answer 4

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

Question 5

what does PTH cause?

Answer 5

increase rna tubular reabsorption and calcium from bone

Decreases reabsorption of phosphate

Stimulates 1alpha hydroxylase in kidney

Question 6

Exaplin vitamin D metaolism?

Answer 6

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.

Question 7

Where is calcitonini ecreted from and what dioes it do?

Answer 7

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

Question 8

Causes of hypocalcaemia?

Answer 8

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

Question 9

Investigation for hypocalcaemia?

Answer 9

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

Question 10

Featurs of hypocalcaemia?

Answer 10

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

Question 11

how to treat hypocalcaemia?

Answer 11

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

Question 12

treat hypoparathyroidism?

Answer 12

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+

Question 13

what is pseudohypoparathyroidism?

Answer 13

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

Question 14

^{what is osteomacia?}

Answer 14

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

Question 15

pathology of osteomlacia?

Answer 15

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

Question 16

featurs of steomaacia?

Answer 16

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

Question 17

who definition of osteoprosis?

Answer 17

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)

Question 18

secndary causes of oteoporosis?

Answer 18

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

Question 19

selective ostogen rceptor moduators?

Answer 19

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

Question 20

list of oral bisphosphonates!

Answer 20

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

Question 21

iv bisphosphonates?

Answer 21

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

Question 22

teriparatide?

Answer 22

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

Question 23

strontium ranelate?

Answer 23

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

Question 24

other therapies?

Answer 24

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

Question 25

pagets?

Answer 25

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

Question 26

how to diagnose pagets?

Answer 26

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

Question 27

bone structure?

Answer 27

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