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- Discussion:
    - due to loss of estrogen & affects postmenopausal women;
    - 2-3% accelerated (loss for 6-10 yrs which then returns to basal loss of 0.3-0.5 %/year;
    - primarily loss of trabecular bone:
           - associated w/ greater decline in medullary bone & preservation of cortex;
           - trabecular-bone loss is three times the rate of normal
           - rate of cortical-bone loss is only slightly above normal;
    - there is accelerated bone loss, decr secretion of parathyroid hormone and increased secretion of calcitonin and functional impairment in 25 Vit D hydroxylase activity;
          - w/ decr production of 1,25(OH)(sub 2)D and therefore decreased calcium absorption;
          - defect in calcium absorption may aggravate bone loss;
    - spine in type I:
         - loss of structural trabeculae weakens vertebrae & predisposes them to acute collapse;
         - vertebral bodies are skeletal elements most at risk of frx in osteoporosis;
         - vertebral fractures are usually of the "crush" type associated w/ large deformation and pain;
    - fractures:
         - vertebral and Colles fractures are common;
         - vertebral body, distal radius contain large amounts of trabecular bone and are prone to fracture;
         - frx occur most frequently in vertebrae, distal aspect of radius, and intertrochanteric region of the femur in type-I osteoporosis;

- Treatment:
    - all pts w/ type I osteoporosis should receive supplemental calcium: 1 to 1.5 gm / day;
    - when high bone turnover is present, cyclic estrogen / progesterone is appropriate;
    - Vit D: 400 to 800 units / day;
    - w/ severe osteoporosis consider use of calcitonin therapy, especially if estrogen therapy is contra-indicated or not tolerated