Which has a higher turnover rate, trabecular or corticol bone?
What are the biochemical markers of bone formation?
-Carboxyterminal propeptide of type I collagen (P1NP)
What are the biochemical markers of bone resorption?
Carboxyterminal of type I collagen (CTX-1)
What is osteoporosis?
a skeletal disorder characterized by compromised bone strength predisposing to fracture. Bone strength reflects the integration of bone density and bone quality
How is osteoporosis measured/tested?
Central DEXA currently the gold standard to measure bone mineral density
What is the risk of a fracture with a DEXA of -1, -2, and -3
These numbers represent standard deviations from normal bone density and the risk doubles per each SD away from the mean
so if O SD= 1 risk
-1= 2x more likely
What DEXA T score is diagnostic of osteoporosis?
-2.5 (from -1 to -2.5= osteopenia) OR
Low-trauma (aka fragility) fracture with a T-score greater (more positive) than -2.5
How much does a single vertebral fracture increase the risk of another? 2 vertebral fractures?
1 vertebral fracture increases risk by 5x (and increases risk of hip fracture by 2x), and 2 increases by 12x
Even at the same T-score, _____ increases the risk of fracture
What drugs increase the risk of fracture?
glucocorticoids, TCAs, SSRIs, PPIs, long-acting benzodiazepines, antipsychotics
anticonvulsants, aromatase inhibitors, androgen deprivation therapy (prostate cancer Tx)
Risk factors for fracture?
Age, previous low trauma Fx, low BMI, current cigarette smoking
steroid use, rheumatoid arthritis, high alcohol intake, fam Hx of fracture
Who should be treated with osteoporotic Tx?
-those with T-score less than 2.5 after age 50
-osteopenia with Hx of a fragility fracture
-Use FRAX score to decide to treat those younger than 50 with a T- or Z-score less than 2.5 or older than 50 with a t-score greater than -2.5
How do you interpret FRAX
A 10-yr risk of 3+% for hip fracture or 20+% for major osteoporotic fracture is sufficient to initiate pharamcological treatment
What things in a osteoporotic patient might suggest Cushing's syndrome being the underlying cause?
chronic steroid use, obesity, accelerated weight gain, buffalo hump
What things in a osteoporotic patient might suggest primary hyperparathyroidism being the underlying cause?
hypercalcemia and an elevated PTH with decreased Phosphate
What things in a osteoporotic patient might suggest acromegaly being the underlying cause?
arthralgias, large hands and feet, obstructive sleep apnea
What things in a osteoporotic patient might suggest secondary hyperparathyroidism being the underlying cause?
What things in a osteoporotic patient might suggest hypogonadism (low testosterone) being the underlying cause?
low libido, erectile dysfunction, loss of muscle mass
What things in a osteoporotic patient might suggest hyperthyroidism being the underlying cause?
suppressed TSH, tachycardia, diarrhea, etc.
How is idiopathic osteoporosis treated?
1) optimize lifestyle (stop alcohol and tobacco, increase physical activity, maintain calcium and vitD(30+ng/mL))
2) Pharm intervention (bisphosphonates, etc.)
What is osteomalacia/rickets?
failure to mineralize bone leading to softening of bone most commonly due to vitD deficiency (nutritional, no sunlight, liver disease)
What is Type I VitD Dependent Rickets?
AR disease caused by a defect in 1a-hydroxylase
What is Type II VitD Dependent Rickets?
AR disease caused by defect in receptor response to activated vitD
What is Paget disease of bone?
localized area of lytic then sclerotic bone formation that leads to formaiton of large amounts of poor quality bone that can manifest as enlarged skull, bony pains, and extremity deformities
Complications: hearing loss, bone tumors (osteosarcoma), fractures
Tx of Paget's disease?
single IV dose (because they have a very long half-life) of bisphosphonates is typically curative
Labs for Paget's disease?
What is osteopetrosis?
Too much brittle bone is made (labs are normal and DEXA will be VERY positive) but breaks like chalk
What is osteitis fibrosa cystica?
disease caused by hyperparathyroidism that is primarily seen in primary hyperpTH and ESRD patients with very high PTH levels.
How does OFC present in labs?
elevated PTH, elevated calcium in primary HPT and normal/low-normal calcium in ESRD patients. Elevated ALP
What is the most sensitive and specific radiologic finding of OFC?
subperiosteal resorption of cortical bone, best seen in high-resolution films of the phalanges. A similar process in the skull leads to a salt-and-pepper appearance
Bone cysts or brown tumors may present as osteolytic lesions