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5 - Chemical Pathology > Calcium > Flashcards

Calcium Flashcards

1
Q

What is the key feature of osteoporosis?

A

Reduced bone mineral density – the bone structure is normal.

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2
Q

What are the common presentations of fractures in osteoporosis?

A

Smith’s fracture (radius fractures forwards, falling onto a flexed wrist)

and Colle’s fracture (radius fractures backward, falling onto an outstretched hand).

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3
Q

What are the risk factors for osteoporosis? (8)

A

Cushing’s
steroids
hyperthyroidism
age
immobility
early menopause
alcohol
low BMI.

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4
Q

What are the blood test findings in osteoporosis patients? (2)

A

Everything is normal

Decreased bone mineralisation (ALP may be raised if a recent fracture occurred)

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5
Q

How is osteoporosis managed? (5)

A

Weight-bearing exercise
Vitamin D

Alendronate (bisphosphonates)

Teriparatide (artificial PTH derivative)

HRT or SERMs (e.g., raloxifene)

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6
Q

What are the blood test findings in osteomalacia/rickets? (3)

A

Low calcium and phosphate
High ALP
High PTH

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7
Q

What are the causes of osteomalacia/rickets? (4)

A

Poor diet
Malabsorption
Renal failure
Lack of sun exposure

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8
Q

How does osteomalacia present clinically? (3)

A

Bone pain

Muscle pain

Increased fracture risk (key feature: pseudofractures, e.g., Looser’s zones)

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9
Q

What causes primary hyperparathyroidism? (3)

A

Parathyroid adenoma (most common)

Parathyroid hyperplasia

Parathyroid carcinoma

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10
Q

What is osteomalacia?

A

Vitamin D deficiency, impaired bone mineralisation and bone structure is ABnormal

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11
Q

What are the bone features in primary hyperparathyroidism? (2)

A

Tends to affect the radius especially

Untreated cases lead to osteitis fibrosa cystica (bony cysts, Brown’s tumors)

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12
Q

What are the blood test findings in familial hypocalciuric hypercalcemia (FHH)? (5)

A

High calcium (mild)
Low phosphate
High ALP
Normal/high PTH
Low calcium in urine

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13
Q

What are the features of secondary hyperparathyroidism? (4)

A

Low calcium
High phosphate
High ALP
High PTH

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14
Q

What are the effects of PTH on calcium and phosphate metabolism?

A

PTH increases calcium reabsorption and phosphate excretion in the kidneys. It also increases osteoclastic activity and activates 1-alpha-hydroxylase for calcium absorption.

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15
Q

What are the main causes of secondary hyperparathyroidism?

A

Renal osteodystrophy (renal failure) and Vitamin D deficiency.

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16
Q

What are the features of tertiary hyperparathyroidism? (2)

A

No longer sensitive to PTH, so high PTH despite high calcium

Caused by CKD leading to autonomous secretion of PTH

17
Q

What are the features of Paget’s disease? (5)

A

Increased bone turnover

Bone pain

Bones may be warm, fractures, cardiac failure

Bowing of the tibia

Hearing loss (both conductive and sensorineural)

18
Q

What are the blood test findings in Paget’s disease? (2)

A

Everything is normal except very raised ALP

Also get a rise in osteocalcin

19
Q

What are the key investigations for Paget’s disease? (2)

A

X-ray

Technetium Bisphosphonate Scan (aka MDB scan): shows diffuse uptake by one bone (Paget’s) or blotchy uptake (metastatic bone cancer)

20
Q

How is Paget’s disease managed? (1)

A

Bisphosphonates (if symptomatic)

21
Q

What are the complications of lung cancer related to calcium metabolism? (2)

A

Produces PTHrP

Causes lytic bone lesions and raised ALP

22
Q

What are the features of pseudohypoparathyroidism? (4)

A

PTH resistance

Associated with a short 4th & 5th metacarpal

Phenotypic picture like Albright hereditary osteodystrophy (obesity, rounded facies, hypogonadism, mild LD)

Bloods: High PTH, hypocalcaemia, high phosphate

23
Q

What are the features of pseudopseudohypoparathyroidism? (4)

A

Normal calcium
Normal PTH
Normal biochemistry

Features of pseudohypoparathyroidism: short stature, brachydactyly, subcutaneous calcification, obesity

24
Q

What are the features of primary hypoparathyroidism? (3)

A

Example: secondary to parathyroidectomy (or DiGeorge syndrome)

Low calcium

Low PTH and high phosphate

25
Q

What are the key points about calcium in general? (5)

A

Important in causing depolarisation (high calcium → failure of depolarisation; low calcium → irritable nervous system)

Normal range: 2.2–2.6 mmol/L

99% stored in the bone; 1% carried in the blood

Corrected calcium (takes into account albumin) is important

Vitamin D supplements = cholecalciferol (Vitamin D3)

26
Q

What are the forms of Vitamin D in humans? (2)

A

Cholecalciferol (Vitamin D3) from UV light

Ergocalciferol (Vitamin D2) from plants

27
Q

What is the pathway for Vitamin D metabolism in the body? (5)

A

UV light converts 7-dehydrocholesterol in the skin to cholecalciferol (Vitamin D3)

Vitamin D3 converted to 25-hydroxycholecalciferol in the liver by 25-hydroxylase

25-hydroxycholecalciferol converted to 1,25-dihydroxycholecalciferol (calcitriol) in the kidneys by 1-alpha hydroxylase

Calcitriol increases calcium & phosphate absorption in the gut

Vitamin D levels measured in blood = levels of 25-hydroxycholecalciferol

28
Q

What are the 4 main causes of hypercalcaemia? (4)

A

Primary hyperparathyroidism (most common)

Bone metastases (common in hospitalised patients)

Sarcoidosis (rare)

Multiple myeloma

29
Q

What are other causes of hypercalcaemia? (6)

A

PTHrP release from cancer (e.g., small cell/squamous cell lung cancer)

Thyrotoxicosis

Hypoadrenalism

Thiazide diuretics

Excess Vitamin D

Sarcoidosis → ectopic 1-alpha hydroxylase (more common in summer; managed with high-dose prednisolone, 40 mg

30
Q

What are the symptoms of hypercalcaemia? (6)

A

Bone: Bone pain, fractures

Stones: Kidney stones (radioopaque on imaging)

Abdominal groans: Diffuse abdominal pain, pancreatitis, constipation

Psychic moans: Depression, lethargy, confusion, seizures, coma

Polyuria, polydipsia

Nephrogenic diabetes insipidus

31
Q

What are the signs of hypercalcaemia? (5)

A

Band keratopathy (calcium deposition across the front of the eye)

Pepperpot skull

Osteitis fibrosa cystica

NOTE: Band keratopathy develops only with chronic hypercalcaemia, commonly due to primary hyperparathyroidism

32
Q

What is the management of hypercalcaemia with calcium levels between 2.6–2.8 mmol/L? (4)

A

No urgent treatment required

Drink lots of water

Avoid thiazide diuretics

Refer to endocrinology for minimally invasive parathyroidectomy (Sesta MIBI scan and ultrasound used to identify overactive glands)

33
Q

What is the management of hypercalcaemia with calcium levels >3 mmol/L or if unwell? (5)

A

Administer 4–6 L of 0.9% IV saline over 24 hours (if liver failure, consider dextrose instead)

First litre should be given rapidly within 1 hour

If no room for more saline, use furosemide

Insert catheter if associated with renal failure

If malignancy + bone pain: use bisphosphonates (e.g., pamidronate)

34
Q

What are the causes of hypocalcaemia? (7)

A

Chronic renal failure

Vitamin D deficiency

Subtotal/total thyroidectomy

Alkalosis
Acute pancreatitis

Congenital absence of parathyroids
(e.g., DiGeorge syndrome)

Magnesium deficiency (involved in PTH regulation)

35
Q

What are the symptoms of hypocalcaemia? (5)

A

Mnemonic: CATS go NUMB
Convulsions
Arrhythmias
Tetany
Numbness (commonly around the mouth)

Other: Chvostek’s sign (facial nerve), Trousseau’s sign (carpopedal spasm), depression

36
Q

How is hypocalcaemia managed? (1)

A

Vitamin D (may need to give activated forms in renal failure)

37
Q
A

5 - Chemical Pathology (7 decks)

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