Osteoporosis is best defined as

• A. Vitamin D deficiency alone
• B. Autoimmune bone destruction
• C. Increased bone mass and density
• D. Skeletal disorder with compromised bone strength and increased risk of fracture

Answer: (D)

Osteoporosis is a skeletal disorder characterized by compromised bone strength that leads to an increased risk of fracture. Bone strength depends on both bone density and bone quality; in osteoporosis, there is a loss of bone mass and deterioration of bone microarchitecture, so the bones become porous and more fragile. This makes fractures much more likely even with minor stresses or falls, which is the key clinical consequence.

Vitamin D deficiency can contribute to weak bones because it impairs mineralization, but it does not by itself define osteoporosis. Autoimmune bone destruction describes a different process where the immune system targets bone or joints, not the generalized weakened bone structure seen in osteoporosis. Increased bone mass and density would actually indicate stronger bones, not osteoporosis.