What is osteoporosis? 

The mechanism of osteoporosis:

A bone is a living tissue that constantly rebuilds itself to maintain its strength. To illustrate, old damaged bone is replaced with healthy new bone "bone remodeling". This renewal is the fruit of the work of two types of cells:

• Osteoclasts which destroy old bone through a process called bone resorption.
• Osteoblasts that make new bone which is bone formation.

Up to about 45 years old, the activities of resorption and formation balance each other and allow the renewal of the bone structure. Meanwhile, with aging, for both women and men, there is a "natural" decrease in bone mass.

Many factors are involved in this regulation. The most famous are :

• Sex hormones (especially estrogens and androgens). Indeed, these hormones control bone remodeling and promote the formation of young bone.
• Vitamin D. A lack of vitamin D can upset this balance.

In some people, this loss of bone mass is without serious consequences. In others, abnormal acceleration of bone resorption not compensated by sufficient bone formation leads to excessive loss of bone mass and strength. Consequently, osteoporosis takes place.

Risk factors of osteoporosis:

Age: As someone ages, age becomes the primary cause of osteoporosis.

Sex: Without doubt, osteoporosis is 2 to 3 times more frequent in women. Menopause is a contributing factor, especially if it occurs early, before the age of 40.

Heredity: A genetic predisposition with the existence of cases of osteoporosis in the family should be taken into account.

Treatments: Many treatments promote the loss of bone density:

• Treatment with high doses of corticosteroids for a period of at least three consecutive months (current or past), for example in the event of rheumatoid arthritis or Crohn's disease

• Certain treatments resulting in a reduction or cessation of the secretion of sex hormones (eg endometriosis treated with antigonadotropes, hormonal treatment for breast cancer, hormonal therapy for prostate cancer, surgical removal of the ovaries or testicles).

Endocrine diseases: It's the delay in treating some endocrine diseases that leads to osteoporosis, such as:

• Hyperparathyroidism or increased secretion of the parathyroid glands (located in the neck and involved in the regulation of calcium and phosphorus metabolism).

• Hyperthyroidism.

Vitamin D deficiency: In particular due to lack of sunshine in winter, in elderly people with reduced mobility and/or calcium deficiency due to insufficient intake or an inappropriate diet (rich in salt, protein and/or coffee), which promotes the loss of calcium in the urine, leads to bone demineralization.

Lifestyle: Exessive thinness (body mass index below 19), lack of physical activity or prolonged immobilization, and exessive consumption of tobacco and alcohol.

How to diagnose osteoporosis:

To make a diagnosis of osteoporosis, a test called bone densitometry can be performed to assess the density of the bones. This exam is painless. The patient lies down on a device that looks like an X-ray table and must remain motionless for a few minutes. The irradiation is twenty times less than for a chest X-ray. Different bones can be studied: the vertebral column, the neck of the femur or the entire skeleton.

Bone densitometry measures bone density and their mineral content. It thus makes it possible to determine the degree of demineralization of the skeleton and the importance of the risk of fracture.

According to the criteria put by the World Health Organization:

• There is osteopenia when bone loss is between 10 and 25%,
• and osteoporosis when bone loss is equal to or greater than 25%.

However, this technique suffers from great variability and its methods of use have not yet been validated.

How to prevent osteoporosis:

The renewal of bone tissue occurs throughout life. The disease is therefore not irremediable and can be prevented by taking care to follow a correct lifestyle.

Eat foods rich in calcium (Dairy products): Calcium is absolutely necessary for good skeletal health. Calcium intake must be sufficient throughout life, but more particularly in the first twenty years. If necessary, the doctor can prescribe calcium supplements during this period.

Limit calcium losses: Eating foods rich in calcium is important, but the proper absorption by the intestines and ceasing the elemination of calcium by urine is still necessary. Oxalates (substances in beets, rhubarb, spinach, sorrel, etc.) and tannins in tea reduce calcium absorption. Avoid consuming these foods at the same time as dairy products. The sodium present in cooking salt would inhibit the action of vitamin D and could also reduce the assimilation of calcium. For example, caffiene (tea, coffee, cola, chocolate) and alcohol promote the elemination of calcium by urine.

Store vitamin D: Vitamin D is mainly synthesized by the skin under the effect of ultraviolet rays. Its role is essential because it promotes the absorption of calcium by the digestive tract. If sun is not possible, taking vitamin D supplements is an option.

Exercise: Physical activity builds bone strength, especially activities that cause small impacts on the bones: running, tennis, hiking, stepping, etc. Physical activity also has the advantage of improving balance, thus minimizing the risk of falls. When the sport becomes difficult, it is necessary to continue to do a little gymnastics at home, to walk often and at a good pace, to take the stairs rather than the elevator. Swimming is useful if you suffer from a compression of the vertebrae.

Stop smoking: Tobacco accelerates bone loss.

Treatment:

Osteoporosis drugs belong to several classes. Whatever the drug used, it must be taken into account that it is a long-term treatment (several years) and whose effectiveness is only manifested in the long term. This should be taken into account in patients with reduced life expectancy.

Bisphosphonates:

Alendronate (Fosamax® and generics), risedronate (Actonel® and generics) and zoledronate (Aclasta® and generics) are effective in the treatment of postmenopausal osteoporosis to reduce the risk of vertebral fracture and hip in patients at high risk of fracture and are reimbursable in this indication. They differ from each other by possible other indications (cortisonic osteoporosis, male osteoporosis, etc.), their tolerance and their precautions for use, their rhythm and their route of administration.

Other drugs:

Denosumab (osteoclast inhibitor monoclonal antibody): It's a second line of treatment (Prolia® S/C/ 60mg). It's important for the treatment of postmenopausal osteoporosis to reduce the risk of vertebral, non-vertebral and hip fractures in patients at high risk of fracture.

Raloxifene: It's effective only on vertebral fractures (Evista® and Optruma® 60 mg tablets). Actually, it's necessary in the prevention and treatment of postmenopausal osteoporosis. In other words, it reduces the risk of vertebral fracture, in patients with spinal osteoporosis at low risk of femoral neck fracture, aged under 70, without thromboembolic risk factor and whose calcium deficiency can be fixed.

Teriparatide: In patients with two or more vertebral fractures (Forsteo® 20 μg/80 μl injection). One of the drugs for the treatment of postmenopausal osteoporosis. This drug reduces the risk of vertebral and peripheral fractures, but not of the hip, in women who already have two vertebral fractures. Also, it treats osteoporosis in men with two vertebral fractures. Moreover, Teriparatide treats cortisone osteoporosis complicated by at least two vertebral fractures in women and men receiving long-term systemic corticosteroid therapy.

Complications:

Certainly, when bone mass decreases below a certain threshold, the bone becomes frail and brittle. Therefore, a trivial fall or, more rarely, a sudden movement can cause a fracture. Furthermore, the most frequent fractures are those of the wrist, vertebrae or femoral neck.

It can be a fall from the height of the person, a simple shock or, rarely, a spontaneous fracture (a bone that breaks on its own).

As a matter of fact, wrist fracture is a frequent indicator of osteoporosis in women over 50.

Vertebral fractures or vertebral compression, are very painful; if they happen again, they lead to a reduction in size and, over time, the appearance of a bump.

After 80 years, it is mainly fractures of the neck and the femur taking place.

References:

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-Kelsey JL. Risk factors for osteoporosis and associated fractures. Public Health Rep. 1989;104 Suppl(Suppl):14-20.

-Armas LA, Recker RR. Pathophysiology of osteoporosis: new mechanistic insights. Endocrinol Metab Clin North Am. 2012;41(3):475-486. doi:10.1016/j.ecl.2012.04.006

-Hanley DA, Adachi JD, Bell A, Brown V. Denosumab: mechanism of action and clinical outcomes. Int J Clin Pract. 2012;66(12):1139-1146. doi:10.1111/ijcp.12022

-Srivastava M, Deal C. Osteoporosis in elderly: prevention and treatment. Clin Geriatr Med. 2002;18(3):529-555. doi:10.1016/s0749-0690(02)00022-8

-Lane NE. Epidemiology, etiology, and diagnosis of osteoporosis. Am J Obstet Gynecol. 2006;194(2 Suppl):S3-S11. doi:10.1016/j.ajog.2005.08.047

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