Osteoporosis is a disease characterized by an excessive weakness of the skeleton, due to a decrease in bone mass and the deterioration of the bone microarchitecture.
It is a disease common in women after menopause because bone mass decreases with age and with the lack of female hormones (estrogen). It affects fewer men than women and exceptional children.
It is a major risk factor for bone fractures (especially hip).
Osteoporosis can be the result of the acquisition of a bone insufficient capital at the end of growth or an excessive bone loss during adult life. Factors genetic, nutritional and environmental determine the acquisition of capital for bone growth and bone loss.
Heredity is the most important determinant of bone acquired at the end of growth.
Blacks, for example, have an average bone density higher than the Caucasian or Asian; girls mother osteoporotic have a lower bone density and are more fractures than girls mother not osteoporotic. There was however unable to identify a single gene for osteoporosis; determinism of osteoporosis is multigenic.
Environmental factors such as a low-calcium diet or insufficient physical activity among adolescents may be responsible for a deficit of acquisition of bone.
Risk factors for developing osteoporosis are:
* Ethnicity and particularly the Caucasian subjects. This is due to a lifestyle (diet rich in calcium, protein and low in vitamin (including vitamin D, B12 and K)
* The high age,
* Low body mass index,
* Family history of fractures of the hip,
* Deficiencies in calcium and protein
* The excessive consumption of tobacco, alcohol, coffee,
* Vitamin D deficiency (lack of sunshine and consumption of plants),
* Physical inactivity, prolonged detention,
* The deficit to sex hormones,
o early menopause induced or spontaneous,
o castration (both sexes) chemical or surgical
o late puberty,
* Certain hormonal diseases hyperthyroidism, hyperparathyroidie, diabetes insulin, hypercorticism (Cushing's disease, ...), hyperandrogénisme, Klinefelter syndrome, Turner syndrome,
* Certain metabolic diseases haemochromatosis, hypercalciuria isolated idiopathic or family ...
* Inflammatory rheumatism: rheumatoid arthritis, ankylosing spondylitis,
* Other chronic diseases: chronic renal failure, hepatocellular failure, cirrhosis, mastocytosis,
* Certain treatments, especially prolonged corticosteroid, GnRH analogues, anti-aromatases.
At the genetic level, several mutations in the genes LPR5 and LPR6 (low-density lipoprotein receptor) seem to be correlated with a slightly increased risk of osteoporosis.
Signs and symptoms
Osteoporosis usually does not sign. His presence significantly increases the risk of fracture. This risk is inversely correlated with bone mineral density.
The diagnosis of osteoporosis based on the measurement of bone mineral density by ostéodensitométrie, using the method most often X-rays DEXA. There is talk of osteoporosis if the density is below 2.5 standard deviations from normal. Between -2.5 and -1 standard deviations, it is called osteopenia.
The bone is renewed throughout life through a process known as "bone remodeling": this remodeling is not at the same time on all surfaces but bone on tiny homes. In these homes remodeling begins with a phase of bone resorption leading to the formation of a cavity, followed by a phase of bone formation during which the cavity is filled by new bone. This process of remodeling is in deficit, ie it has formed a little less bone than it has been eliminated. This balance deficit explains bone loss associated with age, which will lead to osteoporosis if the bone at the end of growth was insufficient or if the activity remodeling a record high deficit. This balance deficit is enhanced by a deficiency or worse absorption of calcium and vitamin D. In women, the decline in the rate of female sex hormones at menopause is a factor. This explains that, on average, loss of bone density becomes sensitive from 50 years for women and 70 years for men, with significant variations depending on individual genetic predisposition of each diet, physical activity . Osteoporosis is common after a prolonged bed rest. It is also a symptom of evil of space.
Often called the "silent epidemic", osteoporosis exposes them to greater risk of fractures, the main danger, including fractures of the hip, wrist and fractures of the spine.
List of diseases associated with osteoporosis
Osteoporosis may be secondary to a condition which can consider setting up a prevention of this bone loss:
* Lack gonadotrope particularly in the following diseases: Turner syndrome, Klinefelter syndrome, anorexia nervosa, insufficient hypothalamic, hyperprolactinemia.
* Endocrine disorders that can be found in: Cushing's Syndrome, hyperparathyroidism, hyperthyroidism, insulin-dependent diabetes, acromegaly,
* Digestive disorders and nutritionels following: malnutrition, prolonged parenteral nutrition, malabsorption syndromes, gastrectomy, sévéres liver disease (such PBC).
* Rheumatic diseases Rheumatoid arthritis, ankylosing spondylitis
* Hématologies diseases including multiple Myeloma, lymphoma and leukemia, mastocytosis, hemophilia, thalassemia.
It is in countries where consumption of milk and milk products is the most important (USA, Finland, Sweden and United Kingdom) that osteoporosis is more prevalent. The Eskimos that absorb the largest amount of calcium in the world (more than 2000 mg / day per fish), the rate of osteoporosis the highest in the world, this because they have a very rich food animal proteins (250 g to 400 g per day). People living in Asia or Africa are not prone to this disease, while consumption of calcium is well below (less than 500mg/jour) recommendations of WHO which recommends consuming 1 000mg calcium per day. The Japanese who consume an average of 300mg calcium / day, as well as the Bantu women who consume 200 to 300 mg, rarely suffer from osteoporosis, which is not true of women in USA: who ingest of 840 to 1340 mg per day! There are 3 times more fractured neck of the femur in the more than 65 years in Los Angeles and Hong Kong. People of Asian origin s'occidentalisant, are subject to ostéoropose, showing that this disease is more due to a lifestyle.
The osteoporosis and its complications have significant economic implications: the cost was estimated at 17 billion dollars in 2003 to the USA.
The main goal of treatment is to reduce the risk of fracture.
The prevention of osteoporosis involves several types of interventions:
* About how life: physical exercise tends to boost bone density subject to submit to the bone twisting forces. This involves the application of loads or shocks: running, gym. In contrast, the landfill activities (swimming, cycling, etc.). Have no significant impact.
* Food: a scheme providing the necessary daily calcium and vitamin D is recommended. This can be supplemented with calcium supplements under medical supervision, particularly among postmenopausal women. The effectiveness of this supplementation on the prevention of fractures is low, without conclusive demonstration. Taking vitamin D would be some efficiency, more clearly demonstrated in relation to its cec similar to that vitamin D native.
The consumption of promoting a product alkaline is recommended as fruits and vegetables, in fact, the calcium is used to reduce the acidity of body products by certain foods such as proteins. A diet rich in protein, increases the acidity of the body that will be rémédié by a release of calcium and therefore a loss calcium!
* Drug treatments have proved effective in preventing fractures. It uses most often bisphosphonates, SERMs (Selective Estrogen Receptor Modulator, class represented by raloxifene) and strontium ranelate. None of these drugs have demonstrated superiority over the other. In severe forms of osteoporosis with several vertebral fractures, one can use the parathyroid hormone injection. The interest of these drugs is not established where a low risk of fracture.
* Hormonal treatment of menopause, the only effective treatment available before 1995, is being discussed because, depending on the products and protocols used (estrogen alone or combined with progestin, hormones or humanized horse, absorption per os or patch .. .) It may expose them to an increased risk of breast cancer and cardio-vascular accident (WHI studies and One million women). The effectiveness on the prevention of fractures is discussed, all the studies failing to show a significant decrease in recent.
The prevention of fractures in the elderly is also based on the prevention of falls.
Read also Menopause