Bones and Calcium Metabolism Flashcards
Effect of PTH
- kidneys
- bones
- small intestines
Effect of PTH
- Kidneys
- Increased calcium reabsorption
- Increased phosphate excretion [Phosphate Sparing Hormone]
- [Stimulates 1 alpha hydroxylase enzyme in kidney that makes PTH]
-
Bones
1. Increased bone resorption - Small intestines
- Increased calcium absorption
- Increased phosphate absorption
Factors increasing calcium metabolism
PTH
Calcitriol/Vit D
Factors decreasing calcium metabolism/blood calcium
Calcitonin
Effect of calcitriol/vitamin D on:
Kidneys
Bones
Small intestine
Effect of calcitriol/vitamin D on:
Kidneys
- Increased calcium reabsorption
- Decreased phosphate reabsorption
Bones
- Increased bone formation
Small intestine
- Increased calcium absorption
- Increased phosphate absorption
Which has a bigger effect on increasing blood calcium, PTH or calcitriol?
Calcitriol
Overall effect of PTH on blood
increased calcium
decreased phosphate
Overall effect of calcitriol on blood
Greatly increased calcium
Decreased phosphate
Where is PTH produced?
Parathyroid glands
Where is calcitriol produced?
Skin {with UV light]
Activated by enzymes in liver [25-hydroxylase] and kidney [1-a-hydroxylase]
[PTH stimulates action of 1-a-hydroxylase]
Where is calcitonin produced?
Parafollicular cells in thyroid
Why is UK population deficient in calcitriol
Less sunlight/UV
SBA 1
63 y o man, generalised bone pain and muscle weakness
What is the most likely underlying diagnosis?
A Osteomalacia
B Primary hyperparathyroidism
C Paget’s disease
D Osteomyelitis
E Osteoporosis
A Osteomalacia
sba 2
A 75 year old woman presents with polyuria, constipation. She admits that her mood has been low over the past few weeks. Her blood results reveal the following:
hypercalcaemia
low phosphate
normal pth
normal glucose
What is the most likely underlying diagnosis?
A Osteomalacia
B Primary hyperparathyroidism
C Paget’s disease
D Osteomyelitis
E Osteoporosis
B Primary hyperparathyroidism
Explain the parathyroid axis
Low calcium
Stimulates production of PTH and Calcitriol/Vit D
Increases blood calcium
Negative feedback decreases production of PTH and Calcitriol/Vit D
Primary hyperpth
definition
pathophysiology
risk factors
symptoms and signs
investigations
- blood
- other
blood results
treatment
Primary hyperPTH
Definition
Excess uncontrolled secretion of PTH from parathyroid adenoma
Pathophysiology
Parathyroid adenoma- no negative feedback
Risk factors
MEN one or two a
Hypertension
Symptoms and signs
Often asymptomatic
Hypercalcaemia- stones, bones, thrones, abdominal groans, psychic moans
investigations
- blood
FBC
CRP
U and E
LFT - ALP
Ca
Phosphate
PTH
Vit D
- other
Imaging:
X-ray/CT- bone disease- Pepper pot skull
CT KUB- renal stones
Cervical US- before surgery
blood results
High Ca, PTH, ALP [or normal PTH, ALP]
Low phosphate
Normal Vit D
Treatment
Surgical- first line= total parathyroidectomy
Medical- Cinacalcet [calcimemetic]
If acute hypercalcaemia:
IV fluids
And if still high: bisphophonates
Secondary hyperPTH/Osteomalacia/Rickets
definition
pathophysiology
risk factors
symptoms and signs
treatment
Secondary hyperPTH
Definition
Hyperparathyroidism in response to low Ca- due to disorder of bone remodelling
Pathophysiology
Low Ca due to low vit D- osteomalacia- PTH is high due to lack of negative feedback
Risk factors
Vitamin D deficiency
- poor diet, poor sunlight, malabsorption
- Chronic kidney disease
- Liver disease
Symptoms and signs
General
Fractures/bone pain- Looser’s pseudofractures
Fatigue
Hypocalcemia- convulsions, arrthymia, tetany, numbness- CATS go numb
Proximal myopathy
Rickets- only in children
Bowed legs
Rachitic rosary
Knock knees
Bone bossing
Investigations
Same as primaryHPT
- Bloods for calcium , PTH etc
- Imaging- X rays, CT KUB, cervical US
Treatment
If acute hypocalcaemia:
IV calcium gluconate
Medical- if due to simple vit D deficiency
Calcium
Vitamin D- inactive- ergocalciferol
Medical- if due to CKD
Treat CKD
Calcium
Vitamin D- active - alfacalcidol
Symptoms of hypocalcaemia
CATS go numb
Convulsion
Arrthymia
Tetany
Parasthesia
Blood biochemistry in different conditions- summary table
Characteristic radiological finding in primary hyperPTH
Pepper Pot Skull
Two radiological findings in secondary hyperPTH
Looser’s pseudofractures
Rachitic rosary
SBA 3
An 82 year old man sees his GP because of a 3 month history of progressive deafness. Using a 512Hz tuning fork, the doctor performed both Weber’s and Rinne’s test. There was lateralisation of vibration to the left ear, and air was louder than bone conduction in both ears. His blood results were normal apart from increased ALP.
What is the most likely underlying diagnosis?
A Osteomalacia
B Primary hyperparathyroidism
C Paget’s disease
D Osteomyelitis
E Osteoporosis
C Paget’s disease
SBA 4
E Osteoporosis
Paget’s disease
Definition
Types
Phases of disease
Aetiology
Risk factors
Symptoms
Signs
Investigations
Blood results
Paget’s disease
Definition
Disease of bone remodelling
Aetiology
Genetic factors
Types
monostotic- one bone- 25%
polyostotic- 75%
Phases of disease
Lytic phase - osteoclast- resorption
Mixed phase- osteoblasts compensate
Sclerotic phase- too many osteoblasts- formation of excess woven bone
Risk factors
Elderly
FH
Symptoms
Often asymptomatic
Bone pain- femur, pelvis, skull
Nerve compression- sensorineural deafness, sciatica
Signs
Bone bossing- skull, femure, tibia
Thoracic kyphosis
Warm skin over painful bone
Investigations
Bloods: FBC, U and E, LFT- ALP, Ca, Phosphate, Vit D, PTH
Serum CTX - bone resorption marker
Serum P1NP - bone formation marker
Imaging: X rays, radionucleotide bone scan- Tec
Blood results
Osteoporosis
Definition
Aetiology
a- primary causes
b- secondary causes
Symptoms
Signs
Investigations
Osteoporosis
Definition
Reduced bone density
Aetiology
Primary causes
Old- over fifty
Post menopausal
Secondary causes
- Drugs- steroids, thyroxine
- Endo- Cushing, hyperthyroidism
- Cancer- multiple myeloma
- MSK- SLE, RA
- GI- Coeliac disease, IBD
Symptoms and Signs
Fractures- Neck of femur
Back pain
Thoracic kyphosis
Investigations
Bloods: FBC, CRP, U+E, LFT-ALP, Ca, Vit D, Phosphate, PTH
Imaging:
X ray
DEXA scan
What is a DEXA scan?
Scan to look at bone mineral density
What is a T score in a DEXA scan?
Patient’s bone mineral density compared to a young healthy adult
What is a Z score in a DEXA scan?
Patient’s bone mineral density compared to an age matched bone mineral density
When calcium is high, PTH should be…?
Low [not normal]
Biochem q1
E Osteoporosis
Biochem q2
Osteomalacia [due to vitamin D/calcitriol deficiency]
Biochem q 3
Osteomalacia [due to CKD]
Biochem q4
B Primary hyperparathyroidism
Biochem q5
B Primary hyperparathyroidism
[PTH is inappropriately normal]
Biochem q 6
C Paget’s disease
Endocrine causes of proximal myopathy
COT
Cushing’s
Osteomalacia
Thyrotoxicosis
Factors predisposing to osteoporosis
Primary:
Old age- over fifty
Post menopausal
Secondary:
Endocrine- Cushing, hyperthyroidism
Drugs: Steroids, thyroxine
MSK- SLE, rheumatoid arthritis
GI- coeliac, IBD
Cancer: multiple myeloma
Symptoms and signs of Paget’s disease
Symptoms:
Bone pain
Sensorineural deafness, sciatica [nerve compression]
Signs
Warm to touch over painful bone
Thoracic kyphosis
Bone bossing- skull, femur tibia
Special markers to investigate in Paget’s?
Serum CTX- bone resorption
Serum P1NP- bone formation
