Metabolic Diseases of Bone Flashcards
What are the metabolic functions of bone
control calcium and phosphate in the body
What factors influence calcium regulation
Parathyroid hormone - output increases increased when calcium level is low. It restores the calcium level to normal by increasing tubular re-absorption from the kidney and mobilising calcium from the bones
Calcitonin - Produced by the C cells of the thyroid gland - it inhibits bone resorption and is secreted in response to a raised serum calcium
Vitamin D - increases calcium absorption in the gut. Increased levels increase calcium and phosphate levels in the serum
How does secondary hyperparathyroidism occur
vitamin D deficiency - the parathyroids are stimulated to restore the calcium levels
What 3 factors can cause bone loss
decreased osteoid formation (osteopenia)
Decrease in mineralisation of osteoid (osteomalacia)
Increase in removal of bone by osteoclasts (osteolysis)
What is vitamin C necessary for
collagen synthesis and osteoid deposition especially at the growing ends of bones
What is the treatment of scurvy
Ascorbic acid
What can cause generalised osteopenia
cushing’s syndrome or steroid therapy
What is osteomalacia
a failure of bone mineralisation which may lead to pain, weakness and fragility f the bone
What are the causes of osteomalacia
lack of vitamin D or calcium (rickets)
Renal tubular acidosis
Parathyroid hormone insufficiency
What is Rickets
The childhood form of osteomalacia - failure of bon e mineral to ossify from lack of vitamin D
This leads to widening of the epiphyseal lines and generalised demineralisation
Epiphyses are widened and have accepted appearance usually best seen on an AP radiograph of the wrist
What are the clinical symptoms of Rickets
age 1 - the child is small and fails to thrive
bowing of the femora and tibiae
large head
deformity of the chest
Describe the biochemical findings in a patient with rickets
serum calcium normal
phosphate low
alkaline phosphatase raised
What is the treatment for Rickets
Vitamin D dose is curative
Can the deformities of rickets be corrected
yes - when the disease is under control
What are the main changes seen in adult osteomalacia
softening of the bones
What patients are more commonly affected by adult osteomalacia
Asian immigrants whose diet may be deficient
What are the clinical features of Osteomalacia
generalised bone pain
anorexia, weight loss, muscle weakness, sometime bony deformities
What are some radiological features of osteomalacia
Diffuse osteoporosis
pathological vertebral wedging and pseudo fractures
How is a diagnosis of osteomalacia made
Serum calcium and phosphate lowered
alkaline phosphatase raised
Iliac crest bone biopsy
What is the treatment for osteomalacia
Vitamin D
What is osteolysis
Loss of mineralised bone due to osteoclastic resorption in excess of deposition
What characterises primary hyperparathyroidism
generalised skeletal porous and the development of cystic lesions filled with soft brown connective tissue
What are the clinical features of primary hyperparathyroidism
Generalised bone pains
indigestion
weakness
anorexia
What are some radiological features of primary hyperparathyroidism
Generalised porous and characteristic localised lessons which are usually well circumscribed in long bones
Pepper pot appearance
How is a diagnosis of primary hyperparathyroidism made
High serum calcium
low phosphate
raised alkaline phosphatase
What is the treatment for primary hyperparathyroidism
parathyroid adenoma may be excised
What is osteoporosis
reduction in bone mineral density as a result of reduced mineral mass as well as a change in the micro-architecture of the bone iteslef
What are some causes of osteoporosis
Dietary deficiency
lack of stress on bone
What are the clinical features of osteoporosis
Bone pains
lassitude and acute ack pain due to pathological vertebral fractures
gradual development of a kyphosis and loss of height
What is seen on Xray in osteoporosis
generalised loss of density of bones and thinning of the cortices from within
ghostly quality
What are the histological features of osteoporosis
Haversian canals are widened and the trabeculae are thin and sparse
What is the treatment for osteoporosis
Encourage exercise and give dietary supplements of calcium, vitamin D and proteins
Calcitonin and bisphosphonates
What is a method of prophylaxis for peri and post menopausal women
HRT
