Metabolic Bone Disease Flashcards
What is osteoporosis?
- Disorder of bone quantity not quality
- Deterioration of microarchitecture, compromised bone strength and increased risk of fractures.
What is paget’s disease of the bone?
Abnormal localised bone remodelling (quality) - a chronic disorder that causes bones to grow larger and become weaker than normal. The disease usually affects just one or a few bones. The bones most commonly affected by Paget’s disease include: Pelvis. Skull.
What causes paget’s disease of the bone and what are its clinical features?
- caused primarily by increased osteoclast resorption, and increased but disorganised bone formation.
- Clinical features include: enlarged skull, bowing of long bones, large joint OA, fracture, nerve compression and possible Deafness
What is paget’s sarcoma?
malignant change to paget’s, most commonly osteosarcoma.
Osteoblastic differentiation and malignant osteoid production, malignancy from mesenchymal cells.
Poor prognosis.
What is the pathophysiology of Paget’s and what 3 phases can it occur in? `
Abnormal osteoclasts/precursors which are greater in number, unusually large and sensitive to simulation.
Lytic = intense osteoclast resorption
Mixed = resorption and compensatory formation
Scleotic = predominant osteoblstic formation.
What investigation and treatment is required for paget’s disease of the bone?
Investigations: radiographs and bone scan; from lab results elevated ALP
Management: OC inhibition e.g. bisphosphonates and arthroplasty when needed.
What is osteopetrosis?
Defective osteoclastic resorption.
Cannot acidify howship’s lacunae, hence bone formed but not remodelled.
leads to dense bone with obliterated medullary canal.
Gives predisposition to low energy transverse fractures, and increases risk of non-union.
What is the prognosis of osteopetrosis?
Prognosis:
The severe infantile forms of osteopetrosis are associated with diminished life expectancy, with most untreated children dying in the first decade as a consequence of bone marrow suppression.
Life expectancy in the adult-onset forms is normal.
What is hyperparathyroidism?
Increased circulating levels of PTH as a result of excess production by one or more parathyroid glands.
What is primary and secondary hyperparathyroidism?
Primary hyperparathyroidism:
Intrinsic abnormality of parathyroid glands leads to pathological increase in PTH production, likely due to parathyroid adenoma.
Secondary hyperparathyroidism:
Increased PTH secretion from hypertrophic parathyroid glands, secondary to chronic hypercalcaemia, hyperphosphatemia, vitamin D deficiency or chronic renal disease.
What are the symptoms of hyperparathyroidism? (10)
“Bones, stones, groans and psychic moans”
- Arthritis
- Osteoporosis
- kidney stones
- Constipation
- GI ulcers
- Acute pancreatitis
- Polyuria
- Forgetfulness
- Depression
- Confusion
What is the treatment for primary and secondary hyperparathyroidism?
- Primary = parathyroidectomy
- Secondary = treat underlying cause, vit d. deficiency most common, renal disease.
What are the main effects of PTH?
- increases bone resorption: OBs release RANK-L and decrease OPG production, allowing OCs to differentiate and activate
- Increase renal hydroxylation of vitamin D: increased production of calcitriol results in increased RANK-L release and increased intestinal and renal uptake of Calcium.
What are the two hydroxylations of Vitamin D and what are the intermediate products?
Liver:
Vit D -> 25 hydroxy vit. D
Kidney:
25 hydroxy vit. D -> 1,25 dihydroxy vit. D = calcitriol
What are the function of calcitriol?
- Increases availability of calcium through increasing GI and renal uptake
- Maintains serum phosphate levels by decreasing PTH synthesis and increasing FGF23 (negative feedback loop)
