14 - Osteoporosis Flashcards
(49 cards)
What does osteoporosis mean?
Porous bones
What is osteoporosis?
- Chronic condition w/ fragile bones
- Change in micro architecture of the bone, cause excessive loss of bone mass
When is osteoporosis most common and in which gender?
Post menopausal women
Can osteoporosis be prevented?
Yes
What are risk factors for osteoporosis?
- Menopause
- Age
- Drugs (ex: glucocorticoids, prolonged use of coumadins)
- Stress
- Genetics
How is bone formed?
Osteoblasts secrete type 1 collage and Ca2+ and PO4- to form hydroxyapatite crystal (aka osteocytes) which connect to other osteocytes
What is the difference between osteoblasts and osteoclasts?
- Osteoblasts build the bone
- Osteoclasts break down the bone
Do bones stay around the entire lifespan of a human?
No, they are constantly remodeled by the process of resorption and reformation
___ are responsible for resorption or erosin
Osteoclasts
____ are responsible for reformation
Osteoblasts
An abnormality in _____ leads to osteoporosis
Abnormality in resorption and reformation balance; excessive osteoclastic activity
How is osteoporosis diagnosed?
- X-ray
- Fragility fractures from minor trauma (ex: sneezing, coughing, bending)
- Bone mineral density assessed be dual X-ray absorptiometry at hip and spine (T score of less than 2.5 = osteoporosis)
What are some strategies for preventing or delaying osteoporosis?
- Weight bearing exercise
- Cessation of smoking and limiting alcohol intake
- Avoid drugs that increase bone loss (ex: glucocorticoids)
- Diet containing calcium and vitamin D and supplements of protein and vitamin K (only if px needs drugs that increase bone loss)
Why do glucocorticoids cause osteoporosis?
- Antagonize vitamin D stimulated Ca2+ absorption
- Stimulate renal Ca2+ excretion
- Block bone collagen formation
What regulates serum calcium levels in the body?
- Calcitonin and parathyroid hormone (PTH)
- Calcitonin decreases and PTH increases serum Ca2+
What is the difference between vitamin D2 and D3?
- D2 = ergocalciferol (plant source)
- D3 = cholecalciferol (animal source)
How does the body get the majority of its vitamin D3?
80-90% is synthesized in the skin
How is vitamin D3 synthesized?
7-dehydrocholesterol (precursor molecule) is cleaved by the energy from UVB light on the skin to form vitamin D3 (pro-hormone)
Are vitamin D2 and D3 active?
No, they are inactive
How is active vitamin D formed?
Hydroxylation occurs in the liver, then final hydroxylation occurs in the kidneys to form 1,25-dihydroxyvitamin D (calcitriol)
What are the effects of calcitriol on bone?
- Increase Ca2+ and phosphate absorption from gut
- Decrease renal excretion of Ca2+ and phosphate
- Increase bone turnover or remodeling
What can cause a deficiency in calcitriol?
- Poor diet
- Inadequate sunlight
- Hereditary receptor resistance
What are some benefits of vitamin D that aren’t related to bone?
- Muscle mass, strength, and balance
- Multiple sclerosis
- Psoriasis
- Immune system
- Anti-type 1 diabetes
- Colorectal cancer
- Asthma
What is the difference between vitamin K1 and K2? What are sources of each vitamin?
- Vitamin K1 required for coagulation; synthesized by plants and green vegetables
- Vitamin K2 involved in bone metabolism; found in meat, fish, and fermented food
