منتدى Rehabilitation Team

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إدارة المنتدى: عامر صدقة
منتدى Rehabilitation Team

    Osteoporosis

    شاطر

    Mansour Nasraween
    عضو مشارك
    عضو مشارك

    ذكر عدد الرسائل : 24
    العمر : 31
    تاريخ التسجيل : 09/07/2008

    Osteoporosis

    مُساهمة من طرف Mansour Nasraween في الثلاثاء يوليو 22, 2008 10:25 am

    Osteoporosis
    - Discussion
    - most common metabolic bone dz
    - definition:
    - what appears to be a characteristic of osteoporosis is an uncoupling of the osteoblastic and osteoclastic processes;
    - WHO definition: a bone mineral density that is 2.5 SD below the mean peak value in young adults of the same race and sex (T-score of -2.5);
    - Z score: bone mineral density compared with the mean value in normal subjects of the same age and sex;
    - Z-score of less than -1 indicates patient is in the lowest 25%, and a score of less than -2 indicates patient is in the lowest 2.5%;
    - bone turnover and bone loss in adults:
    - approx 3 % of cortical bone is replaced each year;
    - approx 25 % of trabecular bone is resorbed & replaced every year;
    - trabecular bone has high surface-to-volume ratio, & 70-85 % of surface of the bone is in contact with bone marrow;
    - after the mid thirties, there is 0.3 to 0.5 % bone loss per year;
    - total bone loss in osteoporosis may exceed 30 to 40%;
    - in early osteoporosis, there will be bone loss of 2-3 % per year (majority occurs in cancellous bone), but this rapid loss may decrease after 6-10 years;
    - risk of fracture:
    - 40% of 50 year old females will have an osteoporotic fracture during their lifetime;
    - in women there is a 15% lifetime risk of hip fracture after age 50 yrs, vs 6% risk in men;
    - vertebral body fractures
    - classfication:
    - type I ("postmenopausal") osteoporosis
    - type II ("senile") osteoporosis
    - secondary osteoporosis:
    - laboratory studies:
    - liver function tests and levels of calcium, albumin, 25-hydroxyvitamin D, intact PTH, and thyroid-stimulating hormone in all patients and
    a total serum testosterone level in men;
    - histology:
    - bone is normal, but there is too little of it;
    - bone that is present is lamellar in character and w/o osteoid seams, resorption cavities, or osteoblastic or osteoclastic activity.
    - specific causes and differential dx of osteoporosis:
    - etiology is multifactorial;
    - references:
    - Bona Fide Genetic Associations with Bone Mineral Density
    - Multiple Genetic Loci for Bone Mineral Density and Fractures


    - Methods to Quantify Osteoporosis:
    - generally osteoporosis is quantified as a percentage of a standard deviation below normal (compared to age matched controls);
    - one standard deviation below normal is mild to moderate where as two standard deviations below normal implies severe osteoporosis;
    - dual X-ray absorptiometry (Dexa) (preferred technique)
    - dual photon absorptiometry
    - single photon absorptiometry:
    - quantitative CT:
    - Singh index:

    - Treatment:
    - first important task is to r/o hyperthyroidism because it represents only truly reversible form of the disease;
    - be sure that patients taking synthroid are not over-medicated;
    - spine in osteoporosis:
    - hip in osteoporosis:
    - younger women: (premenopause)
    - check a thyroid panel since hyperthryoidism is the only reversible form of osteoporosis;
    - normal menstration:
    - calcium: 500 mg of calcium carbonate to be taken orally three times a day;
    - Vit D: 800 units of vitamin D3 PO qd (after determining that the serum Ca is not elevated);
    - amenorrhea
    - menstrual irregularity is often associated w/ stress frxs in female runners.
    - estrogen has protective effects against osteoporosis;
    - female runners who have used birth control pills for over 1 year have a lower rate of stress frxs
    than women who have not used birth control pills;
    - type I (postmenopausal osteoporosis)
    - type II ("senile" osteoporosis)
    - elderly women or men w/ frx of hip & other bones caused by osteoporosis have already lost most of bone they will ever lose;
    - estrogen:
    - there is no convincing evidence that estrogen benefits women over age of 75 years;
    ________________________________________
    - Treatment Agents:
    - vit D:
    - vit-D and calcium supplements will prevent some degree of loss of skeleton and decrease likelihood of frx;
    - 800 units of vitamin D3 PO qd (after determining that the serum Ca is not elevated);
    - references:
    - Calcium plus Vitamin D Supplementation and the Risk of Fractures.
    - estrogen:
    - calcium, estrogen, & calcitonin act by decreasing bone resorption;
    - calcium & estrogen act mainly by decreasing activation of new bone remodeling units (not by decreasing action of existing osteoclasts);
    - estrogen may counteract effect of parathyroid hormone on bone;
    - action may be indirect since bone cells apparently lack estrogen receptors;
    - when estrogen cannot be taken due to concerns about breast cancer, then consider tamoxifen (nolvadex);
    - this is almost as effect as estrogen and is used in the treatment of breast cancer;
    - raloxifene (evista):
    - selective estrogen receptor agonist that activates estrogen receptors in bone tissue and inhibits bone resorption
    w/o stimulating the uterine endometrium;
    - calcium:
    - calcium, estrogen, & calcitonin act by decreasing bone resorption;
    - calcium & estrogen act mainly by decr activation of new bone-remodeling units (not by decr action of existing osteoclasts);
    - national research council's RDA of calcium is 800 mg/day.
    - calcium metabolic balance studies indicate that premenopausal & estrogen-treated women require approx 1,000 mg of calcium / day;
    - dose: 500 mg of calcium carbonate to be taken orally three times a day;
    - postmenopausal women who are not treated w/ estrogen require about 1,500 mg daily for calcium balance;
    - high dietary calcium suppresses age-related bone loss and reduces fracture rate in patients w/ osteoporosis.
    - references:
    - Calcium plus Vitamin D Supplementation and the Risk of Fractures.
    - calcitonin
    - calcium, estrogen, & calcitonin act by decreasing bone resorption.
    - calcitonin may act directly on osteoclasts, which do have calcitonin receptors.
    - calcitonin has recently been shown to be an effective agent in management of patients
    with osteoporosis, although the drug is expensive and difficult to administer;
    - use of drug in inhalant form may make it a more feasible option.
    - biphosphonates:
    - fosamax (alendronate): first line agent;
    - etidronate
    - sodium fluoride: [/right][/left][left]

      الوقت/التاريخ الآن هو الجمعة ديسمبر 14, 2018 4:53 am