What metabolic bone disorder is characterized by loss of bone mass?

The correct answer, osteoporosis, is a metabolic bone disorder primarily characterized by a significant loss of bone mass and density, leading to an increased risk of fractures. This condition arises due to an imbalance between bone resorption and bone formation, where the process of losing bone outweighs the creation of new bone. As a result, bones become weak and brittle, making them susceptible to breaks even from minor falls or injuries.

Osteoporosis is particularly common in older adults, especially postmenopausal women, due to hormonal changes that affect bone density. Symptoms often go unnoticed until a fracture occurs, highlighting the importance of preventive measures, such as adequate calcium and vitamin D intake, along with weight-bearing exercise.

The other conditions listed do not primarily represent bone mass loss. Osteosarcoma refers to a type of bone cancer that affects new bone formation but does not specifically highlight the general loss of bone mass. Osteoarthritis and rheumatoid arthritis are both types of arthritis, which involve joint inflammation and pain but are not classified as disorders that predominantly diminish overall bone density. Hence, osteoporosis is correctly identified as the disorder that characterizes a loss of bone mass.