Hyperparathyroidism Flashcards
Where are the parathyroid glands located
Four parathyroid glands situated posterior to the thyroid gland
What hormone does the parathyroid glands produce?
Produce parathyroid hormone (PTH)
What cells of the parathyroid gland produce parathyroid hormone (PTH)
The chief cells
The chief cells of the parathyroid glands produce parathyroid hormone (PTH) in response to:
a) hypercalcaemia (high blood calcium)
b) hypocalcaemia (low blood calcium)
b) hypocalcaemia (low blood calcium)
What are the 4 ways in which the parathyroid hormone (PTH) raises the blood calcium levels
Increasing osteoclast activity i.e. reabsorbing calcium from bones
Increase intestinal calcium absorption
Increase renal calcium absorption
Increase vitamin D activity by converting vitamin D to its active form
What is the function of vitamin D
Vitamin D acts to increase calcium absorption from the intestines
Define hyperparathyroidism
It is when there is excessive secretion of parathyroid hormone (PTH)
Describe the biochemistry results of primary hyperparathyroidism
High PTH
High Serum Calcium
Describe the biochemistry results of secondary hyperparathyroidism
High PTH
Normal/Low Serum Calcium
Describe the biochemistry results of tertiary hyperparathyroidism
High PTH
High Serum Calcium
Define primary hyperparathyroidism
Excess production of PTH by at least one parathyroid gland causing hypercalcaemia
What is the most common cause of primary hyperthyroidism
Parathyroid adenoma
Name three causes of primary hyperparathyroidism
Tumours e.g. parathyroid adenoma (most common)
Hyperplasia
Carcinoma (rare)
Name the clinical features of primary hyperthyroidism
Asymptomatic or can cause hypercalcaemia
What are the signs of hypercalcaemia
Mnemonic: Moans, Stones, Groans and Psychiatric Moans
- Painful Bones
- Renal Stones
- Abdominal Groans – due to GI symptoms e.g. nausea, vomiting, constipation, indigestion
- Psychiatric Moans – due to effects on nervous system e.g. fatigue, memory loss, psychosis, depression
Name the two investigations for primary hyperparathyroidism
USS of the neck
Parathyroid MIBI scan (uses radiolabelled material to visualise the parathyroid glands)
What is involved in the parathyroid MIBI scan
Involves the injection of radioactive material which is absorbed by hyperactive parathyroid glands. Images can be taken by a gamma camera
What is the treatment for primary hyperparathyroidism
Surgical removal of the tumour or parathyroidectomy
Define secondary hyperparathyroidism
Excess PTH production secondary to hypocalcaemia
What are the two causes of secondary hyperparathyroidism
Vitamin D deficiency
Chronic kidney disease
Describe the pathogenesis of secondary hyperparathyroidism
Vitamin D deficiency or chronic kidney disease causes low absorption of calcium from the intestines, kidneys and/or bones
The parathyroid glands reacts to the low serum calcium by excreting more parathyroid hormone
Overtime this leads to hyperplasia of the parathyroid glands.
How is secondary hyperparathyroidism treated
Vitamin D replacement
OR
Renal transplant
Define tertiary hyperparathyroidism
Autonomous PTH excess due to parathyroid hyperplasia in response to chronic secondary hyperparathyroidism
Describe the pathogenesis of tertiary hyperparathyroidism
Chronic secondary hyperparathyroidism leads to hyperplasia of the parathyroid glands, which can increase in the baseline PTH level
When the cause of the secondary hyperparathyroidism is treated the parathyroid hormone level remains inappropriately high
This high level of parathyroid hormone in the absence of the previous pathology leads to high absorption of calcium in the intestines, kidneys and bones and causes hypercalcaemia.
What is the cause of tertiary hyperparathyroidism
Prolonged secondary hyperparathyroidism
What is the treatment for tertiary hyperparathyroidism
Pharmaceutical
Cinacalcet – mimics the action of calcium on tissues
Surgically
Total or subtotal parathyroidectomy (removal of part or all of the parathyroid tissue returning the parathyroid hormone to an appropriate level)
Risk of hypoparathyroidism requiring calcium supplementation
