Indications for referral- Primary prevention
- Untreated early menopause (<45)
- Low BMI (<19, anorexia)
- Untreated hypogonadism in men
- Aromatase inhibitor treatment
- Vitamin D deficiency/osteomalacia
- Primary hyperparathyroidism/Cushing's syndrome
- Thyrotoxicosis
- Growth hormone treatment
- High alcohol intake
- Liver disease (e.g. PBC)
- Malabsorption (e.g. celiac)
- Oral steroids (daily for >3 months)
- Inflammatory arthropathies
- Kidney dialysis
- Transplant assessment
- Prolonged immobility (>6 months bed ridden)
- Family history (1st degree relative with osteoporosis)
- Secondary prevention
- Follow up scan (usually no sooner than 2-5 years)
- Height loss/kyphosis (>3 cm)
- Vertebral fracture
- Low trauma fracture (e.g. fall from standing position, excluding fingers and toes)
- Radiological evidence of osteopenia
Parathyroid hormone effects
- Bone
- Indirectly stimulates osteoclasts
- PTH stimulates osteoblasts to increase their expression of RANKL and inhibits their expression of osteoprotegerin (OPG)
- OPG binds to RANKL and blocks it from interacting with RANK, a receptor for RANKL
- The binding of RANKL to RANK (facilitated by the decreased amount of OPG) stimulates these osteoclast precursors to fuse, forming new osteoclasts
- Kidney
- Enhances active reabsorption of calcium and magnesium from distal tubules and the thick ascending limb
- Decreases the reabsorption of phosphate, with a net loss in plasma phosphate concentration
- When the calcium:phosphate ratio increases, more calcium is free in the circulation
- Intestine
- Enhances the absorption of calcium in the intestine by increasing the production of activated vitamin D by up-regulating 25-hydroxyvitamin D3 1-alpha-hydroxylase in the kidney
- 1,25-dihydroxy vitamin D increases the absorption of calcium (as Ca2+ ions) by the intestine via calbindin
FRAX
- Gives the 10 year probability of a fracture
- Hip fracture
- Major
osteoporotic fracture (clinical spine, forearm, hip or shoulder fracture)
- Factors:
- Current age
- Gender
- Prior osteoporotic fracture
- Morphometric vertebral fracture,
prior clinical vertebral fracture or a hip fracture is an especially strong
risk factor
- Femoral neck BMD
- Low body mass index
- Oral glucocorticoids for more than 3 months
- At a dose of prednisolone of
5mg daily or more (or equivalent doses of other glucocorticoids)
- Current smoking
- Parental history of hip fracture
- Alcohol intake (3 or more units a day)
- Rheumatoid arthritis
- Secondary osteoporosis
- e.g. - type I diabetes, untreated long-standing hyperthyroidism,
hypogonadism or premature menopause (<45 years), chronic malnutrition, or
malabsorption etc.
Denosumab
- Fully human monoclonal antibody
- Indications:
- Osteoporosis, treatment-induced bone loss, bone metastases, rheumatoid arthritis, multiple myeloma, giant cell tumor of bone
- Designed to inhibit RANKL
- Contraindicated in patients with hypocalcemia
- Sufficient calcium and vitamin D levels must be reached before starting on denosumab therapy
Raloxifene - Oral selective estrogen receptor modulator
(SERM)
- Has estrogenic actions on bone and anti-estrogenic actions
on the uterus and breast
- Used in the prevention of osteoporosis in postmenopausal women
Calcium ranges
- Total calcium
- Ionised calcium
- 1.1-1.4 mmol/L
- Biologic effect of calcium is determined by the amount of ionized calcium, rather than the total calcium
- Ionized
calcium does not vary with the albumin level
- Useful to measure the ionized calcium level when the serum albumin is
not within normal ranges, or when a calcium disorder is suspected
despite a normal total calcium level
- Corrected calcium
- A fall in albumin DECREASES the measured total calcium level
- Each 1 g/dL decrease of albumin will decrease 0.8 mg/dL in measured serum
Ca and thus 0.8 must be added to the measured Calcium to get a
corrected Calcium value
Notes
- Zoledronate is given yearly (5 mg infusion)
- Flu-like symptoms from bisphosphonates
- Activate gamma/delta T cells
- DEXA scan doesn't measure structure, only density
- Steroids preferentially attack certain trabeculae, potentially weakening bone without reducing density
- Z score is used for:
- Very young patients (not yet at peak bone density)
- Very old patients (to check if their low T score is "normal" or not)
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