Osteoporosis
Osteoporosis is a metabolic bone disorder in which the rate of bone resorption accelerates and the rate of bone formation slows. As a result, bone mass decreases. Bones affected by this disease lose calcium and phosphate and become porous, brittle, and abnormally vulnerable to fracture. Osteoporosis may be primary or secondary to an underlying disease.
Primary osteoporosis is classified as idiopathic, type I, or type II. Idiopathic osteoporosis affects children and adults. Type I (postmenopausal) osteoporosis usually affects females ages 51 to 75. Related to the loss of estrogen’s protective effect on bone, type I osteoporosis results in trabecular bone loss and some cortical bone loss. Vertebral and wrist fractures are common. Type II (or senile) osteoporosis occurs most commonly between ages 70 and 85. Trabecular and cortical bone loss and consequent fractures of the proximal humerus, proximal tibia, femoral neck, and pelvis characterize type II osteoporosis. (See Osteoporosis in males, page 636.)
Causes
The cause of primary osteoporosis is unknown. However, clinicians suspect these contributing factors:
mild but prolonged negative calcium balance resulting from inadequate dietary intake
declining gonadal adrenal function
faulty protein metabolism caused by estrogen deficiency
a sedentary lifestyle.
Secondary osteoporosis may result from prolonged therapy with steroids or heparin, bone immobilization or disuse (as occurs with hemiplegia), alcoholism, malnutrition, rheumatoid arthritis, liver disease, malabsorption, scurvy, lactose intolerance, hyperthyroidism, osteogenesis imperfecta, and Sudeck’s atrophy (localized in hands and feet, with recurring attacks).
Gender differencesOsteoporosis in males
Osteoporosis is less common in males than females because of a number of factors. Males have larger skeletons, their bone loss starts later in life and progresses more slowly, and they don’t experience the rapid bone loss due to the decreased estrogen production of menopause. Osteoporosis in males can be classified in three ways.
Primary—idiopathic; having no known cause
Secondary—more common in males than females; may result from drug therapy (anticonvulsants, glucocorticosteroids, warfarin, or long-term heparin therapy), lifestyle factors (alcoholism, immobility, or smoking), or medical conditions (GI disorders, hypercalciuria, hypogonadism, neoplastic diseases, organ transplantation, rheumatoid arthritis, or thyrotoxicosis)
Senile—occurring after age 70; caused by an imbalance in bone breakdown and new bone formation, inadequate calcium and vitamin D intake, and lack of physical activity.
Osteoporosis can be more devastating for males than females, particularly if the condition leads to a hip fracture. It’s estimated that 25% of all hip fractures occur in males, most commonly in the elderly. Males who experience a hip fracture are at increased risk for chronic physical disability and even death.
The evaluation of osteoporosis in males is similar to that in females. Fractures that occur without trauma should always raise the suspicion of osteoporosis. Diagnostic studies for males are the same as those used for females.
The treatment of osteoporosis in males consists of identifying and treating specific causes of bone loss and maintaining a balanced diet with adequate intake of calcium and vitamin D. Preventing bone loss and fractures is of primary importance. Where possible, such risk factors as smoking and alcohol intake should be avoided; an exercise program suitable for the patient should be initiated.
Complications
Bone fractures are the major complication of osteoporosis. They occur most commonly in the vertebrae, femoral neck, and distal radius.
