Calcium And Phosphate Metabolism Flashcards
What is osteoporosis?
- Loss of bone mass - specifically mineral and organic matrix
- Can lead to fragility fractures
State 6 general possible causes of osteoporosis?
- Endocrine
- Malignancy
- Drug-induced
- Renal disease
- Nutritional
- Age
State 4 endocrine causes of osteoporosis?
- Hypogonadism - notably any cause of ostrogen deficiency (e.g. postmenopause)
- Excess glucocorticoids - endogenous or exogenous
- Hyperparathyroidism
- Hyperthyroidism
What is used to diagnosis osteoporosis?
- Measurement of bone mineral density (BMD)
- Uses dual-energy X-ray absorptiometry (DEXA or DXA scan)
State the two types of scores in BMD
State the 4 status of bone density with their ranges?
- Normal: T-score of -1 or above
- Osteopenia: T-score lower than -1 and greater than -2.5 (Intermediate condition between normal + Osteoporosis
- Osteoporosis: T-score of -2.5 or lower
- Severe osteoporosis: T-score of -2.5 or lower, and presence of at least one fragile bone
State 5 possible treatments for osteoporosis with drug names?
- Ensure adequate calcium and vit D intake, appropriate exercise
- Bisphosphonates: inhibit function of osteoclasts: risedronate, alendronate
- PTH analogues
- Denosumab: Human monoclonal antibody against RANK ligand
- Romosozumab: Human monoclonal antibody against sclerostin
- Sclerostin = Inhibitior of Wt signalling which stimulates osteoblast formation
What is meant by menopause and post menopause?
Postmenopause = Menopause is a natural stage in a woman’s life. It occurs in middle age when your body stops ovulating, which causes you to stop having monthly menstrual cycles. This shift occurs because of the change of hormones in your body.
State a possible treatment of osteoporosis as a result of postmenopausal?
- Osteoporosis occurs due to drop in estrogen levels
- Possible treatment = Hormone replacement therapy (HRT) - effects well established but safety of long term treatment was questioned in early 2000s
What is oestomalacia?
- Loss of bone mineralisation = softening of bone
- Called rickets in children
State 7 key symptoms of osteomalacia?
- Permanent deformities in bone growth (rickets)
- Diffuse aches and pains
- Chronic fatigue
- Weak bones
- Low Ca, Pi
- Elevated alkaline phosphatase: Marker for bone turnover
- PTH may be elevated
State the 3 major causes and what is commonly used for treatment of osteomalacia?
- Vitamin D deficiency (most common)
- Mutations leading to errors in vitamin D metabolism (rare)
- Hypophosphataemia
- Treatment most commonly involves ensuring adequate Vit D and Ca
Rare causes of osteomalacia: Hypocalcaemia
State 4 disorders characterised by hypocalcaiemia that lead to osteomalacia?
- Vit. D deficiency
- Renal disease
- 1 alpha hydroxylase mutation -> Vitamin D dependent rickets type 1
- (Point above) a. Enzyme involved in vitamin D conversion (calcitriol), so vitamin D is not formed or at v. low levels
- Vit.d D receptor mutation - Vitamin D dependent rickets type 2
Complete the table
VD
What 3 factors increase Vitamin D (calcitriol) and also descrease it? VD
- Increases by: PTH, Low Ca, Low Pi
- Decreased by: FGF-23, High Ca, High Pi
