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Loss of bone mineral density over time. bone mineral density that is 2.5 Standard deviations or more below the mean peak bone mass as measured by DEXA scan.
Loss of bone mineral density diagnosed by t-score of -1 to --2.5 and is considered precursor to osteoporosis.
occurs when the body fails to form enough new bone, when too much old bone is reabsorbed by the body, or both.
What is bone composed of?
collagen fibers (protein) in a matrix of calcium, phosphate (minerals) and water.
What is the underlying mechanism in all cases of osteoporosis?
an imbalance between bone resorption (osteoclasts breakdown bone and release the minerals, resulting in a transfer of Ca from bone fluid to the blood) and bone formation.
what does bone remodeling consist of?
calcium homeostasis and tissue repair shape and sculpture. In normal bone, there is constant matrix remodeling of bone with up to 10% of all bone mass undergoing remodeling at any point in time.
spongy or cancellous. Most susceptible to metabolic and hormonal influences (metabolically active). Area of growth during childhood and adolescents. The vertebrae, metaphyseal segments of long bones - radius, proximal femur and humerus.
What does demineralization result from?
an imbalance of bone resorption and bone formation (osteoblastic activity)
Causative factors of demineralization?
- disease processes and medication
- non-modifiable risk factors
- modifiable physical activity (mechanical loading) nutritional habits and other lifestyle choices.
How do hormonal factors cause demineralization?
they strongly deterine the rate of bone resorption
How does estrogen as a hormonal factor cause demineralization?
lack of estrogen increases bone resorption as well as decreasing the formation of new bone (impaired osteoblastic activity) that normally takes place in weight-bearing bones.
What happens to bones as a result of lack of estrogen after menopause?
acceleration of bone loss in first feew years. 1% loss after peak bone density (third decade). Accelerated to 2-11% loss for the first 10 years after menopause.
How does testosterone as a hormonal factor cause demineralization?
lower testosterone levels are associated with loss of bone mineral mass. Probably because of a decrease in muscle mass and potentially a decrease in activity.
Osteogenesis Imperfecta (OI)?
brittle bone disease. a genetic bone disorder characterized by defective connective tissue, usually because of a deficiency of Type-I collagen.
Ehlers - Danlos Syndrome?
inherited connective tissue disorders, caused bya defect in the synthesis of type I or III collagen. Reuslts in hyperflexible joints, early OA, muscle fatigue.
a genetic disorder of the connective tissue that affects the skeletal system and often results in long thin limbs.
Cushing's syndrome, hyper/hypoparathyroidism, acromegaly, adrenal insufficiency, type 1 diabetes, malabsorption disorders, pregnancy and postpartum osteoporosis, eating disorders, and any disease that results in the chronic use of corticosteroids, anticoagulants, anticonvulsants and methotrexate (ex: RA, crones, lupus, psoriatic arthritis)
prolonged exposure to high levels of the hormone cortisol
a syndrome that results when the anterior pituitary gland produces excess growth hormone
Celiac disease (decrease absorption of Ca and vitamine D), GI disorders, and Hepatic disease.
Female triad athlete?
most prominent in females participating in sports that emphasize leanness or low body weight. Serious illness with potential lifelong health consequences and can potentially be fatal.
Female triad athlete flow chart?
eating disorder and vigorous training --> low energy availability --> low BMI/LBM --> amenorrhea (decrease in estrogen) --> osteopenia/osteooporosis
can female triad athletes problems be cured by medication?
no pharmacological agent adequately restores bone loss or corrects metabolic abnormalities that impair health and performance in athletes with functional hypothalamic amenorrhea (adversely affects BMD).
eating disorder characterized by severe food restriction. 94% of adolescent females with AN were above average age at start of menarche.
Bone density of girls with AN?
All measures of bone density were lower. BMI, LBM and age of menarche were all strong predictors of BMD. Insulin-like growth factor- I were also significantly lower in girls with AN along with a decrease in estrogen and increase in cortisol.
Four types of post partum osteoporosis that are risk factors for future osteoporosis?
- Idiopathic osteoporosis occurring during pregnancy
- transient osteoporosis of the femur bone during pregnancy
- postpregnancy spinal osteoporosis
- lactation associated osteoporosis.
Corticosteroids adverse effects on bone metabolism that?
- direct inhibition of osteoblast function
- direct enhancement of bone resorption
- inhibition of GI calcium absorption
- increases in urine Ca loss
- hormonal inhibition
- can cause avascular necrosis
non-modifiable risk factors of osteoporosis?
- >50 females >60-70 males
- caucasian, asian, and northern europe ancestry
- early menopause (<45)
- family history
- long periods of immobilization
- disease processes
- use of steroidal medication 3-6 months
- delayed menarche
Modifiable risk factors of osteoporosis?
- physical activity
- maintenance of adequate BW
- minimizing medication
- modify alcohol and tabacco use
bone remodeling is influenced by the level and distribution of the functional strains (external loads) generated within the bone. The trabeculae undergoes the principle adaptive changes.
What happens if the external load on a bone decrease?
the bone will become weaker due to turnover and due to lack of stimulus for the continued remodeling that is required to maintain bone mass.
Best physical activity for osteoporosis?
Regardless of the mode, the stress must be sufficient enough to stimulate bone remodeling/adaptation.
ex: weight-bearing, resistive exercise, aerobic, walking.
resistive exercises effect on bone mineralization?
resistive exercises enhance bone mineralization and play an equivalent, or perhaps greater role, than weight-bearing activities in the management of ostoporosis.resistive exercise also enhance preservation of bone mineral density in the postmenopausal period and in aging males.
What is the most effective type of exercise intervention on bone mineral density for the neck of the femur?
non-weight bearing high force exercise such as progressive resistance strength training for the lower limb.
What is the most effective intervention for BMD at the spine?
combination exercise programs
bone mineralization during walking vs. running?
walking unlike running does not stimulate bone mineralization consistently in the spine or hip
What elicits favorable bone density, muscle strength, and balance adaptations in woler women?
multi-component training program with weight-bearing exercises (training performed twice a week designed to load bones with intermittent and multidirectional compressive forces and to improve physical function)
What is an independent predictor of BMD in the proximal femur, lumbar spine, and forearm?
Besides muscle strength, what else is a positive predictor of bone mineral density?
What is a positive predictor of bone mass at all sites?
in the proximal femur, age was not an independent predictor of BMD at any site.
In postmenopausal women, what is muscle strength a significant predictor of?
bone mass in the femur and forearm, but not in the spine. However, BMI remained predictive of bone mineral at all sites.
summarize the WBV training study.
control group didnt change exercise pattern, resistive training group and WBV group. WBV increased total hip BMD
What does low-frequency vibratory exercise reduces the risk of?
What does low-frequency vibratory exercise reduces the risk of bone fracture more than walking
- S pecific
- A daptations
- I mposed
- D emands
describe resistive exercise.
Resistive exercise is site specific, utilizes principle of overload and wolff's law, and should be done at least two times a week.
Describe weight-bearing exercise.
Remodeling responds best to change in stress distribution. must involve some impact greater than walking, should be done at least 3 times a week.
What is better than both resistive exercise and weight-bearing exercise?
Describe the modifiable risk factor of diet/supplementation
adequate caloric intake to maintain healthy body weight and muscle mass. Avoidance of carbonated drinks and caffeine. Adequate Calcium and vitamin D.
What is the role of vitamin D?
maintain skeletal calcium balance by promoting calcium absorption in the intestines, maintaining calcium and phosphate levels for bone formation, promotes proper functioning of parathyroid hormone.
What do Vitamin D deficiencies result from?
results from inadequate nutritional intake of vitamin D coupled with inadequate sunlight exposure. Absorption disorders. mainly in the elderly, people who get limited sun, obese people.
Clinical manifestations of vitamin D deficiencies?
Osteoporosis, osteomalacia, proximal muscle weakness, and possible increase cancer risk.
recommended intake of vitamin D?
600-800 IU. tolerable 4000IU
What is the most abundant mineral in the body?
- calcium, requirements are highest during adolescents, pregnancy, and post menopause and men over age 65. should consider supplementation.
- 1200-1215 mg/day
Role of calcium in the body?
approximately 99% of the body's Ca is stored in the bones and teeth. The rest has other important uses, such as neurotransmitter release and muscle contraction and conduction of the heart.
What can help prevent osteoporosis in people aged 50 years or older?
the use of calcium or calcium in the combination with vit D supplementation. recommend 1200 mg and 800IU of vitamin D
what can prevent bone loss at the lumbar spine and forearm
vitamin D and calcium supplementation in corticosteroid treated patients but had no affect on femoral neck. Vitamin D alone is not affective.