Disorders of Bone Flashcards
What characterises osteoporosis?
Low bone mass and micro-architectural destruction, producing an increased risk of fracture.
What is the role of osteoclasts?
Bone resorption
What is the role of osteoblasts?
Bone formation
What factors influence bone mass density?
Weight
Sex hormones
Diet
Exercise levels
What are the most common sites for an osteoporotic bone fracture?
Neck of femur
Distal radius
Vertebral body
Humeral neck
What is an example of a fracture common in young people?
Colles’ fracture (caused by FOOSH)
What is an example of a fracture common in the elderly?
Vertebral fracture (often with minimal trauma)
What is a potential complication of a vertebral fracture?
Thoracic kyphosis - this will result in height loss.
What is osteopenia?
A bone mineral density that is > 1 and <2.5 standard deviations below the young adult mean.
What is osteoporosis?
A bone mineral density that is >2.5 standard deviations below the young adult average.
In which patients is a DEXA scan indicated?
Those over 50, with a low-trauma fracture/deemed to be high-risk.
What are causes of secondary osteoporosis?
Cushing’s disease
Coeliac disease
COPD
CKD
What lifestyle changes can improve outcomes for those with osteoporosis?
High-intensity strength training
Low-impact weight-bearing exercise
Avoidance of smoking/alcohol excess
Falls prevention
Increased calcium intake
What pharmacological management options exist for osteoporosis?
HRT
Selective oestrogen modulators
Testosterone replacement (for young men)
Bisphosphonates
What is the first-line therapy in osteoporosis?
Bisphosphonates
If bisphosphonates are contraindicated, what can be given?
Zoledronic acid
Denosumab
What is a rare complication of Paget’s disease?
Osteosarcoma
What genetic bone condition also causes blue sclera?
Osteogenesis imperfecta
It is a disorder of type 1 collagen, and follows an autosomal dominant inheritance pattern.
What should always be considered as a potential cause of repeated fractures during childhood?
Non-accidental injury
What is calcium metabolism dependent on?
Vitamin D
What symptoms are associated with hypercalcaemia?
Bone pain
Kidney stones
Abdominal pain
Psychological disturbances
What are the 2 most common causes of hypercalcaemia?
Primary hyperparathyroidism
Malignancy
How may primary hyperparathyroidism present?
Raised serum calcium
Raised/Normal serum PTH
Raised urinary calcium
Why can malignancy cause hypercalcaemia?
Metastatic bone destruction
Release of PTH-related peptide from a solid tumor
How is hypercalcaemia treated?
Give 4-6L of 0.9% saline, within 24 hours.
May also give a loop diuretic/bisphosphonates (will lower calcium levels in a few days).
What type of scan can be performed to locate a parathyroid adenoma?
Sestamibi scan
When is a parathyroidectomy performed?
End organ damage (e.g. osteoporosis, or gastric ulcer)
Very high calcium levels
Those under 50
eGFR <60ml/min
What is primary hyperparathyroidism?
A primary overactivity of the parathyroid gland, caused by high calcium, and high PTH levels.
What is secondary hyperparathyroidism?
A physiological response to low calcium/vitamin D levels (causing high PTH).
What is tertiary hyperparathyroidism?
When the parathyroid gland becomes autonomous due to years of overactivity (causes very high levels of PTH and calcium).
What condition is almost always seen in those with a MEN1/MEN2 syndrome?
Parathyroid adenoma
What is familial hypocalciuric hypercalcaemia (FHH)?
A condition where serum calcium levels are high, although levels within the urine are low.
It is the result of calcium-sensing receptors becoming insensitive, leading to continuously high PTH levels.
Usually this is asymptomatic, and will follow an autosomal dominant pattern of inheritance.
What are symptoms of hypocalcaemia?
Paraesthesia
Muscle cramps/tetany
Muscle weakness
Fits
Bronchospasm
Chovstek’s sign
Prolonged QT
How is acute hypocalcaemia treated?
Give IV calcium gluconate, 10ml 10% over 10 mins - this will prevent cardiac/respiratory arrest.
What are causes of hyperparathyroidism?
Congenital abnormalities (e.g. DiGeorge Syndrome)
Destruction
Autoimmune disease
Hypomagnesemia
Iron overload
Idiopathic
What are causes of hypomagnesemia?
Alcohol
Thiazide-like diuretics
PPIs
GI upset
Pancreatitis
Malabsorption
Why does hypomagnesemia cause low serum calcium?
As magnesium is required to release calcium from the intracellular compartment.
How does pseudohypoparathyroidism present?
Low calcium
Raised PTH
Due to the development of PTH resistance (a genetic defect of GNAS1).
How does pseudo-pseudohypoparathyroidism present?
Normal calcium levels
Patient will only have symptoms of pseudohypoparathyroidism - no deranged bloods to match clinical picture.
What symptoms are associated with pseudohypoparathyroidism?
Bone abnormalities
Obesity
Subcutaneous calcification
Learning difficulties
Brachdactyly
What is vitamin D deficiency known as in children?
Rickett’s
What is vitamin D deficiency known as in adults?
Osteomalacia
How does osteomalacia present?
Low calcium
Muscle wasting
Dental defects
Tender bones
How can chronic renal disease cause vitamin D deficiency?
As 1-hydroxylase enzymes will not be able to carry out their function.
