Shechar Dworski, BSc
Osteopenia literally means "poverty of bone," while osteoporosis (OP) means "porous bone." The underlying cause of both conditions is a difference in the rate of bone formation and bone loss. Normally, both processes take place at equal rates resulting in a dynamic equilibrium. Bone density peaks during the second or third decade of life and then gradually declines with age, when bone loss exceeds bone formation. Bone is formed in response to physical stresses imposed on it, so excessive loss may occur as a result of immobility. Other causes of excessive loss include hormonal changes, either after menopause, or with excess parathyroid or corticosteroid hormones, or insufficient vitamin D or calcium intake.
In radiological terms, osteopenia refers to an increased radiolucency of bone. The most common cause of this is OP, although there are other causes for osteopenia, such as osteomalacia (so-called "renal rickets", Vitamin D deficiency-related problems), hyperparathyroidism, and some renal diseases. Renal osteodystrophy (or uremic bone disease) is the term for a complex group of bone disorders that occur in patients with chronic renal failure (CRF). Specific radiographic clues for other causes of osteopenia include: looser zones found in osteomalacia, subperiosteal resorption present in hyperparathyroidism, and focal lytic lesions (as seen in disseminated multiple myeloma).