[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Bones, joints and soft tissue](https://durgical.com/en/general-pathology/areas/bone-soft/) › Metabolic bone disease compared

# Metabolic bone disease compared

- Topic

A side-by-side table of the common metabolic bone diseases: what is wrong, how the blood tests look and what the biopsy shows.

Updated Nov 12, 2026

## Key points

- Osteoporosis: all labs normal.
- Osteomalacia from vitamin D lack: low or normal calcium, low phosphate, high PTH, high alkaline phosphatase.
- Primary hyperparathyroidism: high calcium, low phosphate, high PTH.
- Renal osteodystrophy: high phosphate, low or normal calcium, high PTH.
- Paget: isolated high alkaline phosphatase.
- Osteopetrosis: normal labs; the X-ray (dense bones) gives it away.

## What it is

Metabolic bone diseases affect the whole skeleton or large parts of it and are told apart by their mechanism, their blood chemistry and, when needed, a bone biopsy. Osteoporosis is too little normal bone; osteomalacia is matrix that will not mineralize; hyperparathyroidism and renal osteodystrophy are disorders of remodelling driven by hormones; Paget disease is chaotic local remodelling. Students are asked to match the laboratory pattern to the disease.

## Key facts

- Bone remodelling unit: osteoclasts resorb, then osteoblasts refill; RANKL from osteoblasts drives osteoclasts and OPG blocks it.
- Alkaline phosphatase reflects osteoblast activity; it rises whenever bone formation rises (healing fractures, Paget, osteomalacia, high-turnover bone, growth in children).
- Tetracycline double labelling on biopsy measures how fast osteoid mineralizes; slow mineralization defines osteomalacia.
- Bone densitometry cannot distinguish osteoporosis from osteomalacia: both look 'thin'.

## Metabolic bone disease at a glance

| Disease | Main defect | Calcium / phosphate | PTH | Alkaline phosphatase | Biopsy |
| --- | --- | --- | --- | --- | --- |
| [Osteoporosis](https://durgical.com/en/conditions/osteoporosis/) | Too little bone, normally mineralized | Normal / normal | Normal | Normal | Thin, disconnected trabeculae |
| [Osteomalacia and rickets (vitamin D lack)](https://durgical.com/en/conditions/rickets-and-osteomalacia/) | Osteoid does not mineralize | Low or normal / low | High | High | Wide osteoid seams |
| [Primary hyperparathyroidism](https://durgical.com/en/conditions/primary-hyperparathyroidism/) | Excess PTH from the gland | High / low | High | Normal or high | Tunnelling resorption, fibrosis, brown tumours |
| [Renal osteodystrophy](https://durgical.com/en/conditions/ckd-mineral-and-bone-disorder/) | CKD: phosphate retention, low calcitriol | Low or normal / high | High | Often high | High or low turnover, osteomalacia |
| [Paget disease](https://durgical.com/en/conditions/paget-disease-of-bone/) | Chaotic local remodelling | Normal / normal | Normal | Very high | Mosaic cement lines |
| [Osteopetrosis](https://durgical.com/en/conditions/osteopetrosis/) | Osteoclasts do not resorb | Normal / normal | Normal | Normal | Retained calcified cartilage cores |

## Clinical notes

- An older woman with a vertebral fracture and normal labs: osteoporosis; with low phosphate and high alkaline phosphatase: think osteomalacia.
- A raised alkaline phosphatase also comes from the liver; GGT or bone-specific alkaline phosphatase tells the source.

## Memory aid

Normal labs: porosis or petrosis. Phosphate down: malacia or parathyroid. Phosphate up: kidney. Phosphatase alone: Paget.

## Test yourself

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

## Which metabolic bone disease has completely normal calcium, phosphate, PTH and alkaline phosphatase?

Osteoporosis (and osteopetrosis).

## How do primary hyperparathyroidism and renal osteodystrophy differ in phosphate?

Phosphate is low in primary hyperparathyroidism and high in renal osteodystrophy.

## What laboratory finding is typical of Paget disease?

A high alkaline phosphatase with normal calcium and phosphate.

## Why can a DXA scan not tell osteoporosis from osteomalacia?

Both lower the measured mineral density; only labs or a biopsy show unmineralized osteoid.

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[More Pathology questions →](https://durgical.com/en/practice/?f=pathology)

## Elsewhere in DurgiPedia

- [Alkaline phosphatase (ALP) as a lab test](https://durgical.com/en/biochemistry/topics/alkaline-phosphatase-as-a-lab-test/)
- [Calcium regulation: PTH, vitamin D and calcitonin](https://durgical.com/en/physiology/calcium-regulation-pth-vitamin-d-and-calcitonin/)

## Connections

## Related 5

- [Osteoporosis](https://durgical.com/en/general-pathology/osteoporosis/)
- [Rickets and osteomalacia](https://durgical.com/en/general-pathology/rickets-and-osteomalacia/)
- [Bone in hyperparathyroidism and renal osteodystrophy](https://durgical.com/en/general-pathology/bone-in-hyperparathyroidism-and-renal-osteodystrophy/)
- [Paget disease of bone](https://durgical.com/en/general-pathology/paget-disease-of-bone/)
- [Primary hyperparathyroidism](https://durgical.com/en/general-pathology/primary-hyperparathyroidism/)

## Related conditions 5

- [Osteoporosis](https://durgical.com/en/conditions/osteoporosis/)
- [Rickets and osteomalacia](https://durgical.com/en/conditions/rickets-and-osteomalacia/)
- [Primary hyperparathyroidism](https://durgical.com/en/conditions/primary-hyperparathyroidism/)
- [CKD-mineral and bone disorder (renal osteodystrophy)](https://durgical.com/en/conditions/ckd-mineral-and-bone-disorder/)
- [Paget disease of bone](https://durgical.com/en/conditions/paget-disease-of-bone/)

[← All of general pathology](https://durgical.com/en/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](https://medlineplus.gov/osteoporosis.html) (MedlinePlus, US National Library of Medicine, 2025); [Osteomalacia: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000376.htm) (MedlinePlus, US National Library of Medicine, 2025); [Paget's Disease of Bone | MedlinePlus](https://medlineplus.gov/pagetsdiseaseofbone.html) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/metabolic-bone-disease-compared/