Osteoporosis - Causes and Risk Factors
Osteoporosis is an osteopathy characterized by the quantitative reduction of bone mass (the amount of bone mineral in particular calcium is reduced) per unit of volume and by alterations in the microarchitecture of the bone with consequent increased bone fragility and increased risk of fractures from trauma minimum.
Bone has a mineralized protein matrix consisting mainly of type I collagen, proteins, calcium phosphate and hydroxyapatite crystals. The main cells of bone are osteoblasts and osteoclasts. The former are used for the apposition of calcium at the level of the bone tissue while the latter for the reabsorption of calcium. of calcium in the diet, to maintain calcium homeostasis in the ideal physiological position for the maintenance of vital functions linked to blood calcium, through bone resorption. Also important is the modeling during growth, that is the physiological recorrection that occurs above all in the long bones during growth which takes place under the control of the growth hormone (GH) and partly also of the thyroid hormones.
It must be remembered that bone is a complex structure that must respond to two characteristics: it must be strong enough to withstand the body load and weights of a certain entity, but at the same time it must also be light to allow locomotion and movement. in an easy way.
Also very important is the role of parathyroid hormone (PTH), which has a "direct action on the bone". It is a hormone secreted by the four parathyroid glands, located laterally above and below the thyroid. The secretion is regulated through the perception of the amount of calcium that is present in the blood thanks to a transmembrane receptor called G receptor present on the parathyroid gland. If there is a reduction in the percentage of calcium in the blood, there is an increase in the secretion of PTH. In this way, the PTH serves to regulate the absorption of calcium in the diet and possibly to a reabsorption of calcium from the bone.
Osteoporosis Diagnosis
The WHO defines osteoporosis using the T-score parameter. This parameter represents the patient's bone density expressed as the number of standard deviations (SD) above or below the bone density of a young adult. By young adult we refer to a subject of about 35 years of a certain ethnic group, with a normal state of health and normal physical activity and who has a certain bone density, that is the mineral quantity contained in the bone. The decrease in value below this parameter it allows us to know if we are in conditions of osteopenia (modest reduction in bone mineral content) or frank osteoporosis, which can be more or less important and which puts us at risk of bone fractures at the slightest trauma.
The technique that allows the diagnosis of osteoporosis is bone densitometry. The most used method is dual-energy X-ray densitometry (DEXA) which allows the evaluation of the amount of both trabecular and cortical bone. The DEXA allows the measurement of the bone mineral content at the level of the lumbar spine, the proximal femur and the entire skeleton. Bone density is expressed with respect to the peak bone mass with respect to the control subject.
Osteoporosis
T-score <a -2.5 SD
Osteopenia
T-score between -1 and -2.5 SD
Normal
T-score <a -1 SD
The risk of fracture at any age is mainly determined by skeletal mass. Skeletal mass is related to the maximum mass achieved at maturity and the subsequent percentage and duration of bone loss.
As for the peak of bone mineral density, which is the maximum amount of bone mineral accumulated over the course of one's life, this reaches its highest value around 35 years. It can be influenced not only by genetic factors but also by environmental factors such as: normal calcium intake with the diet, normal and constant physical activity, normal exposure to ultraviolet radiation which favors the maturation of vitamin D.
Causes and risk factors
Osteoporosis is divided into primary, typical of postmenopausal and senile age, and secondary caused by non-bone diseases, drugs (mainly corticosteroids) and toxic substances.
Women are most affected by this problem: for example in the United States 25 million people suffer from it, of which 90% are female. The greater incidence of the disease in women with increasing age is related to the decrease in estrogen, which occurs in menopause, although it is not known exactly how this hormone exerts a protective action against osteoporosis. the most accredited hypothesis is that estrogens favor the uptake of calcium by the bones and inhibit their destruction, with consequent loss of calcium. Man is more protected, both because he has some estrogen production, and because he has a level of testosterone that lasts almost all of his life, which is partly converted into estrogen. This causes men to lose from the age of 50 onwards. 0.4% of body calcium per year, while in women from the age of 35 the loss is already double the male value. In addition, for women, the problems increase with the advent of menopause, because the ovaries stop producing estrogen, which is not compensated by the small amount that is still produced by muscles, fat and connective tissue. Estrogen drops suddenly, with less absorption of calcium in the intestine, a lower production of calcitonin which inhibits demineralization, with the total result that menopause significantly accelerates osteoporosis. With menopause, calcium loss accelerates at a rate of 3-6% per year in the first five years, then decreases to "1% per year". At this rate, a woman loses about 15% of her bone mass in the first five years. ten years after the onset of menopause and at age 70, the decline can reach around 30%.
The causes that can lead to osteoporosis are: reduced calcium intake with diet, reduced physical activity with associated load, ingestion of drinks with reduced calcium content (carbonated drinks), reduced estrogen secretion, stress, reduction of cooked foods home but rich in preservatives and prepackaged, female age over 45, menopause, cigarette smoking, sedentary lifestyle, reduced consumption of dairy products, absence or delay of pregnancy and even breastfeeding. In the vast majority of cases, not a single , but more risk factors contribute to the onset of osteoporosis.
