- Specific Causes:
    - loss of estrogen:
          - in most women there is a rapid increase in bone loss after menopause;
          - this probably results from primarily by loss of estrogen;
          - however, all postmenopausal women have lost estrogens, but not all develop postmenopausal osteoporosis.
    - dietary calcium deficiency: (dietary causes of osteomalacia);
          - note that there are women who have very low calcium intakes who do not develop osteoporosis;
    - hyperthyroidism
    - hypogonadism
    - acromegaly
    - Cushing's syndrome
    - malnutrition
    - medications: anticonvulsants, heparin, cyclosporin A, and chemotherapy;

- Differential Dx:
    - transient osteoporosis of the hip;
    - scurvy
    - osteogenesis imperfecta
    - multiple myeloma
    - lymphoma
    - sickle cell anemia
    - hyperparathyroidism
    - osteomalacia
    - homocystinuria
    - hypermetabolic resorptive osteoporosis