osteoporosis
Osteoporosis is the silent thinning of bone until it becomes fragile enough to break under everyday stress. Picture a once-solid sponge whose walls have grown thin and full of holes: the bone keeps its outer shape but loses the internal struts that give it strength, so a minor fall or even a cough can crack it.
It develops when bone resorption outpaces bone formation over years, so the skeleton is steadily depleted. Hormones are central: after menopause the drop in estrogen unleashes osteoclasts and accelerates loss, which is why it is so common in older women; excess cortisol, low testosterone, and overactive thyroid or parathyroid glands also weaken bone. Peak bone mass built in youth, plus calcium, vitamin D, and weight-bearing exercise, set how much reserve a person has to lose.
The disease is usually painless until a fracture occurs, classically in the hip, spine, or wrist, and hip fractures in particular carry serious risk in the elderly. Bone density is measured by a DXA scan. Treatment combines lifestyle and drugs: most medicines slow resorption (bisphosphonates, denosumab), while a few actively build bone (teriparatide, romosozumab).
An older woman fractures her hip after a minor stumble; a DXA scan confirms osteoporosis driven largely by the estrogen loss of menopause.
A fragility fracture often is the first sign of osteoporosis.
Osteoporosis (too little bone tissue of normal composition) differs from osteomalacia (normal amount of bone but poorly mineralized, usually from vitamin D deficiency); the two need different treatments.