Osteoporosis and low bone mass are currently estimated to affect 44 million Americans, with that figure rising to 61 million by 2020. Some 55% of people over the age of 50 are diagnosed with osteoporosis. Osteoporosis is responsible for more than 1.5 million fractures annually at a cost of $17 billion dollars in 2001. Connexin 43 is the major connexin in bone cells, osteocytes and osteoblasts. Cellular communication via these connexins is essential for the health of bone cells and the transfer of mechanical signals among them that makes for strong, healthy bone. Parathyroid hormone is known to be critical for bone formation and increases both Cx43 levels and their function, whereas a known precipitator of osteoporosis-metabolic acidosis-closes connexins. Even bone health depends on connexin function.
Osteoporosis is a disease of bone - leading to an increased risk of fracture. In osteoporosis bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered. Osteoporosis as defined by the World Health Organization (WHO) in women when bone mineral density is 2.5 standard deviations below peak bone mass (20-year-old sex-matched healthy person average) as measured by Dual energy X-ray absorptiometry (DEXA, DXA. Osteoporosis is most common in women after menopause, but may develop in men and premenopausal women. Osteoporosis can be prevented by lifestyle modifications.
Signs, Symptoms, and Associations
Osteoporosis has no specific symptoms. Osteoporotic fractures can be a hallmark of osteoporosis and typically occur in the vertebral column, hip and wrist.
An increased risk of falling associated with aging leads to fractures of the wrist, spine and hip and may indicate the presence of osteopenia or osteoporosis.
The most important risk factors for osteoporosis are advanced age (in both men and women) and female sex; estrogen deficiency following menopause is correlated with a rapid reduction in BMD, while in men a decrease in testosterone levels has a comparable (but less pronounced) effect. While osteoporosis occurs in people from all ethnic groups, European or Asian ancestry predisposes for osteoporosis.
Smoking of tobacco, low body mass index, low calcium and vitamin D intake, alcoholism, insufficient physical activity, pre and post menopausally, and people who are bedridden are at significantly increased risk for developing osteoporosis.
Diseases and disorders associated with osteoporosis
There are many disorders associated with osteoporosis:
Hypogonadal states, such as Turner's syndrome, Klinefelter's syndrome, Kallmann's syndrome, anorexia nervosa, hypothalamic amenorrhea, hyperprolactinemia and estrogen deficiency.
Other endocrine disorders Cushing's syndrome, hyperparathyroidism, thyrotoxicosis, hypothyroidism, insulin-dependent diabetes mellitus, acromegaly, and adrenal insufficiency.
Nutritional and gastrointestinal disorders such as malnutrition, parenteral nutrition, malabsorption syndromes (e.g. coeliac disease, Crohn's disease), gastrectomy, severe liver disease (especially primary biliary cirrhosis) - those with an otherwise adequate calcium intake can develop osteoporosis due to the inability to absorb calcium.
Rheumatologic disorders such as rheumatoid arthritis, ankylosing spondylitis
Hematologic disorders/malignancy such as multiple myeloma, lymphoma, leukemia, mastocytosis, hemophilia, and thalassemia.
Inherited disorders of the bone such as osteogenesis imperfecta, Marfan syndrome, hemochromatosis, hypophosphatasia, glycogen storage diseases, homocystinuria, Ehlers-Danlos syndrome, porphyria, Menkes' syndrome, epidermolysis bullosa, and Gaucher's disease.
Medications associated with osteoporosis
Medication - for medication potentially causing osteoporosis, the positive effects of them needs to be compared with the degenerative effects on bone.
Steroid-induced osteoporosis arises due to use of glucocorticoids - analogous to Cushing's syndrome and involving mainly the axial skeleton. The synthetic glucocorticoid prescription drug prednisone is a main candidate after prolonged intake.
Barbiturates and some other enzyme-inducing antiepileptics - these probably accelerate the metabolism of vitamin D
Proton pump inhibitors are drugs that inhibit the production of stomach acid and may interfere with calcium absorption.
Anticoagulants - long-term use of heparin is associated with a decrease in bone density and warfarin (and related coumarins) have been linked with an increased risk in osteoporotic fracture in long-term use.
Thiazolidinediones (drugs used for Type II diabetes) - rosiglitazone and possibly pioglitazone, inhibitors of PPARγ, have been linked with an increased risk of osteoporosis and fracture.
Diagnosis
The diagnosis of osteoporosis is made on measuring the bone mineral density (BMD). The most popular method is dual energy X-ray absorptiometry (DXA or DEXA). In addition to the detection of abnormal BMD, the diagnosis of osteoporosis requires investigations into potentially modifiable underlying causes; this may be done with blood tests and X-rays. Depending on the likelihood of an underlying problem, investigations for cancer with metastasis to the bone, multiple myeloma, Cushing's disease and other above mentioned causes maybe performed.
Dual energy X-ray absorptiometry
Dual energy X-ray absorptiometry (DXA, formerly DEXA) is considered the gold standard for the diagnosis of osteoporosis. Osteoporosis is diagnosed when the bone mineral density is less than or equal to 2.5 standard deviations below that of a young adult reference population. This is translated as a T-score. The World Health Organization has established the following diagnostic guidelines:
Related Topics: Causes of Osteoporosis How to prevent Osteoporosis