Hyperparathyroidism Bone Disease
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Direct answer
Hyperparathyroidism bone disease, also called osteitis fibrosa cystica, is skeletal damage caused by excess parathyroid hormone, most often from a single parathyroid adenoma. The hormone drives osteoclast activity, so bone resorption outpaces formation and the skeleton shows subperiosteal erosion, brown tumours and a salt-and-pepper skull. Removing the hormone excess, usually by parathyroidectomy, is what allows the bone to recover.
What you must remember
- Cause: primary disease is most often due to a parathyroid adenoma, while secondary disease arises in chronic kidney disease or vitamin D deficiency.
- Mechanism: raised PTH stimulates osteoclasts, so resorption exceeds formation and bone turnover rises sharply.
- Subperiosteal resorption: erosion along the outer cortex, classically on the radial side of the middle phalanges and at the distal clavicle.
- Brown tumours: expansile lesions filled with haemorrhagic, haemosiderin-rich tissue that usually regress once the hormone excess is cured.
- Salt-and-pepper skull: a granular skull pattern from patchy resorption and fibrosis of the calvarium.
- Biochemistry: in primary disease, calcium and PTH are raised while phosphate is low, and alkaline phosphatase rises with bone turnover.
- Treatment: parathyroidectomy for the adenoma, with the risk of hungry bone syndrome and hypocalcaemia in the days after surgery.
A stepwise approach to a bone lesion in suspected hyperparathyroidism
A patient with bone pain, a fracture or a jaw swelling may show the first sign of a hormonal disorder rather than a primary bone tumour. Following these steps prevents unnecessary surgery on a lesion that will regress once its cause is treated.
- Check calcium and PTH: Hypercalcaemia with a raised PTH points to primary hyperparathyroidism, whereas a raised PTH with low calcium suggests a secondary cause. Phosphate and vitamin D levels help separate the secondary causes further.
- Survey the skeleton: Radiographs of the hands, clavicles and skull reveal subperiosteal resorption and the granular skull.
- Identify brown tumours: An expansile lytic lesion in a patient with high calcium should raise suspicion of a brown tumour before a primary bone tumour is considered.
- Localise the adenoma: Neck ultrasound and sestamibi scintigraphy identify the overactive gland before surgery, and four-dimensional CT is used in selected cases. Localisation matters because a single adenoma is removed in most patients, whereas multiple gland disease needs a wider operation.
- Operate and recheck: Parathyroidectomy lowers calcium and PTH, and the bone lesions regress over months to years.
Where the exam tries to catch you
Most errors come from mistaking a hormonal bone disease for a primary or metastatic lesion.
- Trap: treating a brown tumour by curettage alone Correct: the lesion regresses once the hormone excess is cured, so the adenoma is the real target.
- Trap: reading a granular skull as diffuse metastasis Correct: a salt-and-pepper skull signals high bone turnover, so the next step is to check calcium and PTH.
- Trap: assuming a normal serum calcium excludes the diagnosis Correct: normocalcaemic primary hyperparathyroidism exists, so PTH and vitamin D status must be measured before the diagnosis is dismissed.
Frequently asked questions
Which blood test separates primary from secondary hyperparathyroidism in bone disease?
Calcium is the key discriminator. Primary hyperparathyroidism shows raised calcium with raised PTH and low phosphate, whereas secondary hyperparathyroidism from chronic kidney disease shows low or normal calcium, raised PTH and high phosphate.
What is a brown tumour in hyperparathyroidism?
A brown tumour is an expansile, giant cell-rich lesion of bone that forms where high osteoclast activity destroys normal bone. Its brown colour at surgery comes from haemorrhage and haemosiderin deposition. Most brown tumours shrink after the parathyroid adenoma is removed, so direct surgery on the lesion is rarely needed.
Why does hungry bone syndrome occur after parathyroidectomy?
Hungry bone syndrome occurs because the skeleton, which has been remineralising rapidly, takes up calcium and phosphate from the blood after the adenoma is removed. The result is hypocalcaemia that appears in the first days after surgery. Patients with severe bone disease and high alkaline phosphatase are at greater risk.
Which skeletal sites show subperiosteal resorption in hyperparathyroidism?
Subperiosteal resorption in hyperparathyroidism classically affects the radial side of the middle phalanges, the distal clavicle and the medial aspect of the proximal tibia. Hand radiographs are the most common way to identify it. Recognising these sites is a frequent NEET-PG image question.
Why is alkaline phosphatase raised in hyperparathyroidism bone disease?
Alkaline phosphatase is raised because osteoblasts are stimulated along with osteoclasts, which reflects high bone turnover. It is a marker of activity rather than of the underlying cause. Its fall after parathyroidectomy helps show that the bone is healing.