Parathyroid Pathology Flashcards
What is the main function of the parathyroid gland?
Calcium regulation, through PTH.
Describe the normal pathology of the parathyroid gland. (Location, functional cell type etc.)
Four glands at periphery of thyroid
- Functional cells = chief cells
- Secrete PTH - released in response to low serum calcium
Actions of PTH
- Bone resorption
- Renal tubular resorption of calcium
- Increased conversion of Vit D to active form
- Vitamin D promotes calcium resorption from small intestine
What are the acute and chronic causes of hypocalcaemia?
Acute - usually due to damage/removal of parathyroid during thyroid surgery.
Chronic:
- Chronic renal failure
- Vit D deficiency
- Intestinal malabsorption of calcium
Symptoms of hypocalcaemia?
Hypocalcaemia = neuromuscular irritability.
Calcium usually blocks sodium channels, without calcium there is lower depolarisation threshold and thus irritability:
CATs go numb
- Convulsions
- Arrhythmias
- Tetany
- Numbness
Mechanisms of hypercalcaemia?
Hyperparathyroidism
- Accelerated bone resorption
- Excessive GI absorption
- Decreased renal excretion)
How does a disrupted Ca/PO4 homeostasis cause hypercalcaemia?
Retention of phosphate inappropriate actively feedback loop leading to increased PTH secretion.
Occurs in renal failure
Clinical manifestations of hypercalcaemia:
“Stones, bones, abdominal groans and psychiatric moans”
- Renal stones
- Bone pain
- Abdo - nausea, vomiting, constipation
- Moans - lethary, fatigue
4 classifications of hyperparathyroidism and their meaning
Primary HP - Excess PTH production
- Feedback independent
Secondary HP - Other disease process drives increase in PTH
- Normal feedback mechanisms
- Glands become hyperplastic
Tertiary HP - Autonomous PTH secretion caused by long standing secondary HP
- Abnormal feedback mechanisms
- Autonomous nodule in hyperplastic glands
Ectopic Secretion - PTHrP (PTH-related-protein)
- Malignancy causing secretion
- All 4 glands become atrophic
- Feedback independent
Two primary causes of hyperparathyroidism?
PT adenoma
PT hyperplasia
How common is hypoparathyroidism?
not at all
What is the major cause of hyperparathyroidism?
90% of HP - parathyroid adenoma
What is MEN1?
Inherited condition associated with tumours of the endocrine glands- particularly PT.
ASsociated with multiple nodular PT adenoma and familial PT hyperplasia.
In terms of how much of the parathyroid gland/s are affected, what is the difference between PT adenoma and PT hyperplasi?
PT adenoma = usually solitary gland affected
PT hyperplasia = usually all glands involved (chief cells)
What is the cancer associated with the PT?
Parathyroid carcinoma - tumour of the epithelium, rare.
