Parathyroid Flashcards
What do the lower parathyroids develop from?
3rd branchial pouch
Below level of inferior thyroid artery usually at inferior pole of thyroid gland
Most common cause of primary hyperparathyroidism ?
Adenoma - 80%
How are parathyroid adenoma’s localised?
- Technitium thallium scan
- Sestamibi scan nuclear scan
- Selective venous catheterisation
- PTH assay
What is the thymus derived from?
3rd pharyngeal pouch
What happens in DiGeorges syndrome?
The 3rd and 4th pharyngeal pouches fail to develop
What does PTH do?
- Increase bone resorption - stimulation of osteoclast
- Increase calcium reabsorption in Distal tubule
- Decreased reabsorption of phosphate in proximal tubule
- Increased phosphate excretion in urine
Signs of high calcium?
- Dyspepsia
- Polyuria
- Nocturia
- Constipation
- Depression
Vitamin D
- 1,25-DihydroxycholeCalciferol - active form of vitamin D
- Produced in proximal tubule
- Stimulates calcium absorption in small intestine and renal absorption of calcium
Superior parathyroid
Forth branchial pouch
First trachial ring at the level where the recurrent laryngeal nerve crosses inferior thyroid artery
Blood supply to parathyroid
Inferior thyroid artery
Venus drainage of parathyroid
Thyroid venous plexus to left brachiocephalic vein
What type of cell produces parathyroid hormone
Chief cell
What is the half life of parathyroid Hormone
2-5min
Degraded liver circulation and kidney
Secondary hyperparathyroidism
- Renal failure
- Malabsorption
Normocalcaemia
Elevated phosphate
Elevated parathyroid hormone
Tirtiary hyperparathyroidism
Parathyroid gland becomes hyperplastic due to secondary hyperparathyroidism and continues to produce parathyroid hormone in the presence of normal calcium levels
Bone alkaline phosphatase
Glycoprotein found on surface of osteoblasts
Vitamin D excess
High calcium
High Phosphate
Low parathyroid hormone
Pagets disease
Normal calcium and phosphate
High alkaline phosphatase
Normal Parathyroid hormone
Osteomalacia
Lowish to normal calcium
Low phosphate
High Alkaline phosphatase
High parathyroid hormone
Hypoparathyroidism
- Paresthesia in lips (circumural numbness) and fingers
- Carpopedal spasm
- Tetany
- Cramps
- Dystonia
- Psychosis
- Chvostec sign
- Trousseau sign
- Prolonged QT
Chvostec sign
Twitching of facial muscle
Trousseaus sign
Spasm of fingers and wrist when when BP cuff is tightened for 3 min at 10-20mmhg higher than systolic BP
Treatment of hypocalcaemia
10ml of 10% calcium gluconate over 5min (0.05mmol/kg/hr)