Bone Metabolism Flashcards
What are the parathyroid glands responsible for?
4 glands responsible for the synthesis and release of parathyroid hormone
What are osteoclasts and osteoblasts.
Osteoclasts - decalcify and digest bone matrix liberating calcium
Osteoblasts - synthesis of extra cellular bone matrix and priming it’s subsequent mineralisation
What are the physiological effects of PTH?
- Regulation of Ca concentration in the plasma
- Ca concentration controlled by PTH and calcitriol and calcitonin
How does PTH work?
- Low levels of Ca in blood stimulates the release of PTH from the parathyroid glands
- This causes efflux of Ca from bone, decreased Ca loss in urine and increased absorption of Ca from intestine
How would you test parathyroid function?
- Calcium levels
- Phosphate levels
- Plasma PTH levels
Where is calcitonin secreted from?
Thyroid gland in response to increase in plasma Ca
What are the physiological effects of calcitonin?
- Minor role in regulating Ca levels
- Bone - inhibits osteoclast activity - decreases release of Ca and phosphate in blood
- Kidney - decreased Ca and phosphate reabsorption - decreased blood concentration
What is hyperparathyroidism?
Excessive release of PTH
What causes hyperparathyroidism?
- Primary - parathyroid adenoma
- Secondary - chronic renal failure
- Inadequate nutrition
What are the symptoms associated with increased plasma Ca?
- Thirst
- Increased urine output
- Constipation
- Memory impairment
- Long term - bone pain, osteoporosis, fractures and kidney stones
How would you diagnose hyperparathyroidism?
- Increased plasma Ca
- PTH increased
- Normal phosphate in mild cases, decreased in more severe disease
How would you treat hyperparathyroidism?
- Treat underlying cause - surgery
- Correction of hypercalcaemia
- rehydration with IV NaCl 0.9% - first line treatment - increases GFR and therefore increases urinary Ca excretion to 4-6 litres/24 hours
- bisphosphonates - impair function of osteoclasts decreasing plasma Ca levels - pamidronate disodium IV
What is hypoparathroidism?
Failure if the parathyroid gland to secret PTH or failure of PTH action at tissue level causing decreased plasma Ca and increased plasma phosphate
What causes hypoparathyroidism?
- Post operative
- Multiple endocrine deficiency
What are the symptoms of hypoparathyroidism?
Mainly due to hypocalcaemia
- Numbness and tingling in extremities and mouth
- Muscle spasm
- Irritability
What are the investigations of hypoparathyroidism?
- Decreased plasma Ca
- Increased phosphate
- Decreased PTH
How would you treat hypoparathyroidism?
- Hypocalcaemic tetany
- Ca gluconate IV
- ECG monitoring
- caution in cardiac glycosides - digoxin
- monitor Ca levels
- commence oral supplements immediately
- Chronic treatment
- oral Ca supplement
- vit D preparations
Oral Ca supplements…
- Used alone in mild diesease
- More severe disease - combination with vit D
- Take between meals to avoid binding to dietary phosphate
- S/E’s are bradycardia, arrhythmias and constipation
Vitamin D….
- Main treatment for more severe disease
- Increase intestinal Ca absorption
- Calcitriol or alfacalcidol
- restores normal Ca levels within one week
- effects last 1 week following withdrawal
What is pagets disease
Disturbance of bone remodelling caused by excessive bone resorption by osteoclasts and increased in formation of poor quality bone
New bone is…
Structurally enlarged and weakened with heavy calcification
Paget’s disease mainly effects…
Skull and long bones - femur and tibia
What are the symptoms of Paget’s disease?
- Bone pain
- Joint pain
- Fractures
- Hearing loss
- Blindness
What is the treatment for Paget’s disease?
- Analgesics for symptomatic relief
- Bisohosphonates
- Calcitonin
