Hyperparathyroidism

Question 1

Definition of hyperparathyroidism

Answer 1

Hyperparathyroidism refers to a condition where there is an overproduction of parathyroid hormone.

Question 2

Pathophysiology of primary hyperparathyroidism

Answer 2

Caused by uncontrolled parathyroid hormone produced directly by a tumour of the parathyroid glands (independent of calcium levels). This leads to hypercalcaemia.

caused by a single parathyroid adenoma which happens either because of a genetic mutation in a single cell or because of an inherited disorder e.g. multiple endocrine neoplasia.

Rarely caused by hyperplasia or parathyroid carcinoma

Question 3

Pathophysiology of secondary hyperparathyroidism

Answer 3

Insufficient vitamin D or chronic renal failure leads to low absorption of calcium from the intestines, kidneys and bones. This causes hypocalcaemia. This is usually due to kidney issues as the kidney can’t filter out the phosphate or make active vitamin D.

parathyroid glands reacts to the low serum calcium by excreting more parathyroid hormone. Over time the total number of cells in the parathyroid glands increase as they respond to the increased need to produce parathyroid hormone.

serum calcium level will be low or normal but the parathyroid hormone will be high.

Question 4

Pathophysiology of tertiary hyperpathyroidism

Answer 4

happen when secondary hyperparathyroidism continues for a long period of time.
> leads to hyperplasia of the glands.

The baseline level of parathyroid hormone increases dramatically.

when cause of secondary hyperparathyroidism is treated parathyroid hormone level remains inappropriately high > leads to high absorption of calcium in the intestines, kidneys and bones > hypercalcaemia

Question 5

What does hypercalcaemia lead to?

Answer 5

• Excess calcium makes neurons less excitable, which leads to slower muscle contractions, and diminishes neuron firing in the central nervous system.

Question 6

What is hypercalciuria

Answer 6

This is because there is just too much calcium to be reabsorbed by the kidneys. Excess loss of calcium in urine can lead to dehydration.

Question 7

Clinical manifestations of Hyperparathyroidism

Answer 7

‘Stones, thrones, bones, groans, and psychiatric overtones’

• Stones: kidney stones or gallstones
• Thrones: refers to the toilet, polyuria that results from impaired sodium and water reabsorption.
• Bones: bone pain
• Groans: refers to symptoms of constipation, nausea and vomiting
• Psychiatric overtones: depressed mood, fatigue, psychosis and confusion

Question 8

Investigations for primary hyperparathyroidism

Answer 8

Bloods: high levels of parathyroid hormone; testing for blood levels of calcium, phosphate, and vitamin D to confirm the type of hyperparathyroidism.
- 24 hr urinary calcium:raised
- ALP: raised from bone activity
Imaging e.g.

• DEXA scan for osteoporosis
• ## Can show osteitis fibrosa cystica

Question 9

Differential diagnosis for hyperparathyroidism

Answer 9

Malignant hyperparathyroidism: parathyroid related protein produced by some squamous cell lung cancers, breast and renal cell carcinomas. This can mimic PTH and lead to hypercalcaemia.

Question 10

Management of primary hyperparathyroidism

Answer 10

• If mild, increase fluid intake, avoid thiazides and high Ca2+ intake
• Surgical removal of the tumour
• Calcimimetics: drugs that imitate the action of calcium by attaching to the calcium-sensing receptors on parathyroid cells

Question 11

Management of secondary parathyroidism

Answer 11

• Correcting the vitamin D deficiency
• Phosphate binders
• Renal transplant to treat renal failure
• Sometimes parathyroidectomy

Question 12

Management of tertiary parathyroidism

Answer 12

Surgical removal of parathyroid tissue

Question 13

Secondary and tertiary hyperparathyroidism

Answer 13

Renal osteodystrophy: bone resorption - 2ndary only
Calcification in blood vessels and soft tissues: the high levels of phosphate cause it to stick to any available calcium, forming bone-like crystals.
- Bone resorption:
- Bone fractures
- Osteoporosis
- Osteopenia
- Nephrolithiasis
- Iatrogenic
- Hypoparathyroidism
- Recurrent laryngeal nerve damage

Question 14

Primary hyperparathyroidism diagnostic criteria

Answer 14

Cause: Tumour
PTH: High/ normal
Calcium: High
Phosphate: Reduced

Question 15

Secondary hyperparathyroidism diagnostic criteria

Answer 15

Cause: Low Vit D or CKD
PTH: High
Calcium: Low or normal
Phosphate: Increased

Question 16

Tertiary hyperparathyroidism diagnostic criteria

Answer 16

Cause: Hyperplasia
PTH: High
Calcium: High