Osteoporosis

Lesion

In osteoporosis bone is normal in quality but there is too little of it, so vertebrae, hips and wrists break with minor falls.

Updated Nov 12, 2026

What it is

Osteoporosis is a loss of bone mass with a normal ratio of mineral to matrix, severe enough to raise the risk of fracture. It reflects the balance between the peak bone mass reached in early adulthood and the rate of loss afterward. Postmenopausal oestrogen loss increases osteoclast activity through cytokines and RANKL, while aging reduces the replicative capacity of osteoprogenitor cells and osteoblast function. Secondary osteoporosis comes from glucocorticoids, endocrine disease, malabsorption, immobilization and other causes.

Structure

Trabeculae are thin, perforated and lose their horizontal cross-struts; the spaces between them widen.
Cortices thin and become porous with enlarged Haversian canals.
Osteoid seams and mineralization are normal; osteoclast activity may be increased early after menopause and low in senile disease.
Vertebral bodies collapse into wedge or crush shapes; the thoracic spine bends forward (dowager hump).

Step by step

Bone mass peaks in early adulthood, set by genes, nutrition (calcium, vitamin D), exercise and sex hormones.
From then on, resorption slightly exceeds formation in each remodelling cycle.
After menopause, oestrogen loss raises RANKL and inflammatory cytokines and lowers OPG, so osteoclasts resorb more.
With age, fewer osteoblasts form and each makes less bone; reduced physical activity removes mechanical stimulus.
Trabecular connectivity is lost and cortices thin until ordinary loads cause fractures.

Primary osteoporosis compared

Feature	Postmenopausal	Senile (age-related)
Who	Women in the first years after menopause	Men and women in older age
Main mechanism	High-turnover resorption from oestrogen loss	Low-turnover: fewer, weaker osteoblasts
Bone mostly lost	Trabecular	Trabecular and cortical
Typical fracture	Vertebral body, distal radius	Femoral neck and hip

Clinical notes

Silent until a fracture; vertebral fractures cause back pain, loss of height and kyphosis.
Hip fracture in older people carries high mortality within a year and loss of independence; preventing falls matters as much as bone density.
Latin America: an aging population makes hip fracture a growing burden, and access to densitometry is uneven.
Antiresorptive drugs (bisphosphonates, denosumab against RANKL) and anabolic agents (PTH analogues) are the treatment classes.

In the lab

DXA bone densitometry: a T-score of minus 2.5 or lower defines osteoporosis; between minus 1 and minus 2.5 is osteopenia.
Calcium, phosphate, PTH and alkaline phosphatase are normal in primary osteoporosis; abnormal values point to another disease.

Test yourself

Think of the answer, then tap the question to see it.

Is mineralization abnormal in osteoporosis?

No. The bone present is normally mineralized; there is just less of it.

How does oestrogen loss increase bone resorption?

It raises IL-1, IL-6, TNF and RANKL and lowers OPG, so more osteoclasts form and live longer.

What is the most common drug cause of secondary osteoporosis?

Long-term glucocorticoids.

Which fracture typifies senile osteoporosis?

The hip, mainly the femoral neck.

Add to my cards (4)

Elsewhere in DurgiPedia

Connections

← All of general pathology

Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Osteoporosis | MedlinePlus (MedlinePlus, US National Library of Medicine, 2025); Osteoporosis in Females (StatPearls (NCBI Bookshelf), 2025); Consensus statement: osteoporosis prevention and treatment in Latin America-current structure and future directions (Archives of osteoporosis, 2025).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.