Hyperparathyroidism Flashcards
Definition of hyperparathyroidism
Hyperparathyroidism refers to a condition where there is an overproduction of parathyroid hormone.
Pathophysiology of primary hyperparathyroidism
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
Pathophysiology of secondary hyperparathyroidism
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.
Pathophysiology of tertiary hyperpathyroidism
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
What does hypercalcaemia lead to?
- Excess calcium makes neurons less excitable, which leads to slower muscle contractions, and diminishes neuron firing in the central nervous system.
What is hypercalciuria
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.
Clinical manifestations of Hyperparathyroidism
‘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
Investigations for primary hyperparathyroidism
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
Differential diagnosis for hyperparathyroidism
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.
Management of primary hyperparathyroidism
- 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
Management of secondary parathyroidism
- Correcting the vitamin D deficiency
- Phosphate binders
- Renal transplant to treat renal failure
- Sometimes parathyroidectomy
Management of tertiary parathyroidism
Surgical removal of parathyroid tissue
Secondary and tertiary hyperparathyroidism
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
Primary hyperparathyroidism diagnostic criteria
Cause: Tumour
PTH: High
Calcium: High
Secondary hyperparathyroidism diagnostic criteria
Cause: Low Vit D or CKD
PTH: High
Calcium: Low or normal
