Osteopenia - Causes and Symptoms

Definition

Osteopenia is the reduction of bone mass; it produces thinner and weaker bones.

Within certain limits, osteopenia is to be considered part of the natural aging process; the bone tissue, in fact, over the years undergoes a progressive quantitative and qualitative reduction.

The bone mass remains stable at the maximum values between the 3rd and 4th decade of life, during which osteogenesis is roughly equal to bone resorption. After this period, the activity of the osteoblasts (cells responsible for the formation of new bone) begins to shrink, while that of the osteoclasts (cells assigned to osteolysis) remains at the previous levels. The epiphyses, the vertebrae, the maxillary bones and the mandible undergo a greater loss of mass, with consequent fragility of the limbs, reduction in height and loss of teeth.

Often osteopenia occurs in the years immediately after menopause and is linked to the natural decrease in estrogen, a hormone that is also necessary for normal bone metabolism. In this case we speak of porotic osteopenia, that is linked to alterations of hormones (including parathormone and calcitonin) which regulate the balance between production and bone resorption.

Another form is malacic osteopenia, in which osteoblasts regularly produce the matrix, which, however, is not sufficiently enriched with calcium salts (examples: rickets in childhood and osteomalacia).

Displastic osteopenia, characterized by an altered osteogenesis in a very early phase (eg imperfect osteogenesis) and necrotic osteopenia, due to local microcirculatory alterations (osteonecrosis), can be distinguished.

The main metabolic pathologies of the bone that determine bone hypodensity are osteoporosis (reduced bone mass with altered architecture) and osteomalacia (disordered bone mineralization).

Primary osteoporosis can be senile (related to aging) or post-menopausal (post-menopause). Secondary osteoporosis, on the other hand, can derive from underlying medical conditions, including malabsorption, hypogonadism, hyperthyroidism, multiple myeloma and protracted use of some drugs, especially corticosteroids.

Osteomalacia, on the other hand, is due to reduced mineralization, generally caused by a severe deficiency or an altered metabolism of vitamin D (eg dietary deficiency, malabsorption deriving from gastro-intestinal diseases, chronic renal failure and secondary hyperparathyroidism).

More rarely, osteopenia is found in the context of cystic fibrous osteitis, a condition caused by hyperparathyroidism and characterized by marrow fibrosis. Other factors that increase the risk of osteopenia are prolonged immobilization (for example after a fracture), calcium deficiency, excessive thinness, alcohol abuse and cigarette smoking.