Bone and Biochemistry

Question 1

Summary of Bone Pathology

Answer 1

Bone composition/cells
Investigations of Bone disease

Bone Diseases:

• Osteoporosis
• HPT
• Paget’s, -Osteomalacia/Rickets
• Mets

Ca/Mg/Pi homeostasis

Question 2

State 4 functions of bone.

Answer 2

Structural support
Protection
Produce blood cells
Store minerals (esp Ca)

Question 3

Bones are HIGHLY VASCULAR & are constantly remodelling. Describe the 4 structural components of bone.

Answer 3

Outer: Cortical bone
Inner: Trabecular bone
Cells: (3)
ECM: Ca + minerals = hydroxypatitie

Question 4

Which bone cell produces hormones to comm with other bone cells & produces osteoid?

Answer 4

Osteoblast

Question 5

Markers for osteoblast activity and therefore bone formation?

Answer 5

P1NP

ALP

Question 6

Which bone cell regulated ECM turonver & has mechanosensory properties?

Answer 6

Osteocytes

Question 7

Osteoclasts breakdown bone and have a ruffled border. What regulates them?

Answer 7

PTH
Clacitonin
IL-6

Question 8

As we age our bone becomes less dense. Who are most suseptibly to a quicker decrease in bone density and therefore osteoporosis?

Answer 8

Early menopause women

Question 9

State 4 commonly used investigations in bone disease.

Answer 9

X-ray (gross)
DEXA (density)
Bone markers
Biopsy

Question 10

Name the bone formation and bone resorption markers.

Answer 10

Bone formation: P1NP,
ALP (also in HPT, growth spurt, preg, fractures, Paget’s

Bone resorption: CTX, NTX (increases in periods of high bone turnover)

Question 11

DEXA uses radiation through which bones to assess density?

Answer 11

Lumbar spine

Hip

Question 12

A T-score in DEXA of

Answer 12

OSTEOPOROSIS

Question 13

A normal T-score in DEXA is over what value?

Answer 13

> -1

Question 14

Osteoporosis has numerous risk factors. List 5 main ones.

Answer 14

Female
Early menopause
Smoking
Alcohol
Long-term steroids
Vit D def
UC
RA
UC

Question 15

2” causes of osteoporosis involve conditions from which systems?

Answer 15

Endocrine
GI
Haematological
Respiratory
RA
CKD
Drugs

Question 16

Osteoporosis presents as increase biconvavity in T vertebral bodies, vertebral fractures and a hunched back. T/F?

Answer 16

T

Question 17

Common complication of osteoporisis is…?

Answer 17

Fragility fractures

FRAX tool

Question 18

Bone mets can be lytic or osteoblastic. Presentation?

Answer 18

Signs of hypercalcaemia
Pain
Pathological fractures
Numbness/paralysis, diff urinating (sc mets*)

Question 19

1” HPT is often seen in Females, >45yrs. What are the 4 possible causes?

Answer 19

Adenoma
Parathyroid carcinoma (rare)
Glandular hyperplasia
Ectopic adenoma

Question 20

1” HPT is often ASYMPTOMATIC. What are other possible presentations?

Answer 20

Symptoms of hypercalcaemia

Renal: stones, CKD

Bone: Osteoporosis

Proximal muscle wasting

Question 21

Investigations for 1” HPT?

Answer 21

Imagine: Tc99 Sestambi

Biochemistry (high PTH, high ca, low Pi, High ALP)

Question 22

Treatment for 1” HPT?

Answer 22

Calcimimetics

Surgery

Question 23

2” HPT is caused by what?

Answer 23

Vit D def
CKD (kidneys activate Vit D)

(High PTH, Low Ca)

Question 24

Which type of HPT is present in prolonged 2” HPT (usually CKD)?

Answer 24

3” HPT

Question 25

Which type of HPT is present in prolonged 2" HPT (usually CKD)?

Answer 25

3" HPT

Question 26

The presentation of hypercalcamaemia is described using what mneumonic?

Answer 26

BONES, STONES, GROANS & MOANS

Question 27

Mild symptoms of hypercalcaemia?

Answer 27

``` Polyuria/Polydispia Anorexia Nausea Constipation Mood changes ```

Question 28

Severe symptoms of hypercalcaemia?

Answer 28

``` Abdo pain Vomiting/dehydration Pancreatitis Arrthymias Coma ```

Question 29

State the most common non-PTH and PTH mediated causes of hypercalcaemia.

Answer 29

Non-PTH - malignancy (Sarcoidosis, hyperthyroid, acromegaly) PTH - 1" HPT

Question 30

Vit D def, hypoparathyroidism, Hypoproteinaemia, Reduced dietary intake and EDTA contamination can all cause what?

Answer 30

Hypocalcaemia

Question 31

Ca is needed for what functions?

Answer 31

``` Muscle contraction Neuronal excitability Blood clotting Enzyme activity Bone ECM ```

Question 32

[Ca] is regulated by the Kidneys/Gut/Bone. What 2 molecules also feature in Ca metabolism?

Answer 32

PTH | Vit D

Question 33

Does Acidosis lead to hypercalcaemia or hypocalcaemia?

Answer 33

Hypercalcaemia H+ displaces Ca

Question 34

Mg is an intracellular ion that is essential in metabolism of what other ions?

Answer 34

Ca - Releases PTH K+ - reabsorption in kidneys *ALWAYS CONSIDER HYPOKALAEMIA/HYPOCALCAEMIA with Mg def*

Question 35

Mg is used for what in the body..?

Answer 35

``` Neuromuscular excitation Cofactor ATP Enzyme activity Aids PTH release Aids K+ reabsorption ```

Question 36

Name 3 causes of hypomagnesia. | common in hospitals

Answer 36

Renal Drugs: Gentamicin, chemo, Diuretics GI: Malnutrition/Malabsorption, IV nutrition, diarrhoea

Question 37

Hypomagnesia can cause muscle weakness, decrease CV contractility, ataxia, hyperreflexia etc.. T/F?

Answer 37

T

Question 38

Phosphate is an intracellular ion involved in intracellular signalling. What are some of its functions?

Answer 38

``` ATP component Cellular metabolism DNA backbone Bone ECM Cell membrane ```

Question 39

What hormone controls [Pi]?

Answer 39

PTH Promotes excretion

Question 40

Pi def can lead to muscle weakness, general cellular dysfunction. Severe def can lead to what?

Answer 40

RESPIRATORY FAILURE

Question 41

Causes of Pi def?

Answer 41

HPT Reduced dietary intake Excess loss: renal, GI, Diabetes (diuresis) Refeeding syndrome