CPM Flashcards
How is osteoporosis diagnosed?
→Measurement of bone mineral density (BMD)
→Dual-energy X-ray absorptiometry (DEXA or DXA scan)
What are the stages of osteoporosis?
→osteopenia
→osteoporosis
→severe osteoporosis
What are the causes of osteoporosis?
→Hypogonadism – notably any cause of oestrogen deficiency
→Excess glucocorticoids – endogenous or exogenous- Cushing’s syndrome
→Hyperparathyroidism- excess resorption
→Hyperthyroidism
Why does oestrogen decreased after menopause?
→no more follicles
What are the treatments for osteoporosis?
→Bisphosphonates
→PTH analogues
How is osteoporosis treated in postmenopausal?
→HRT
How does Denosumab treat osteoporosis?
→human monoclonal antibody against RANK ligand
What is bisphophonate?
→inhibit function of osteoclasts: risedronate, alendronate- reduce rate of bone turnover
How does romosozumab treat osteoporosis?
→human monoclonal antibody against sclerostin
→Sclerostin inhibits Wnt signalling
What is osteomalacia?
→Loss of bone mineralization
What are symptoms of osteomalacia?
→Permanent deformities in bone growth (rickets)
→Diffuse aches and pains
→Chronic fatigue
Weak bones
What is elevated in osteomalacia?
→Elevated alkaline phosphatase- enzyme marker for bone turnover
What is a difference between osteoporosis and osteomalacia?
→osteoporosis is when there is loss of organic and mineralisation
What are the causes of osteomalacia?
→Vitamin D deficiency (most common), lack of Vit D supplements or sunlight exposure
→Mutations leading to errors in vitamin D metabolism (rare)
→Hypophosphataemia
In VitD deficiency, what are the levels of Ca, Pi, 25OHD3, 1,25OH, PTH?
→Ca- low →Pi- low →25 OH D3- low →1, 25 OH D3- normal →PTH- high
In renal disease, what are the levels of the hormones?
→Ca- low →Pi- high →25 OH D3- normal →1, 25 OH D3- low →PTH- very high
In 1a hydroxylase mutation (Ricket’s type 1)?
→Ca- low →Pi- low →25 OH D3- normal →1, 25 OH D3- normal →PTH- high
In 1a hydroxylase mutation (Ricket’s type 2)?
→Ca- low →Pi- low →25 OH D3- normal →1, 25 OH D3- very high →PTH- high
What is VitD dependent rickets type 1?
→1α hydroxylase mutation1
What is VitD dependent rickets type 2?
→Vit D receptor mutation
What are the three disorders as a result of osteomalacia and hypophosphataemia?
→X-linked hypopho-phataemic rickets
→Autosomal dominant hypopho-phataemic rickets
→Oncogenic osteomalacia
Which cells secrete FGF23?
→osteocytes
Why does mutation in FGF23 cause excess phosphate excretion?
→Mutation changes proteolytic sequence so FGF-23 remains in circulation for longer
What are the clinical manifestations of renal osteodystrophy?
→Impaired Pi excretion
→High plasma Pi
→Impaired Vit D activation
→Low plasma Ca because of less absorption
→PTH rises
→Excess bone resorption
→May be augmented by acidosis (impaired renal H+ excretion
What does acidosis favour?
→bone mineralisation
